Season 12 (show/hide)
24	The Stockholm Syndrome	2019-05-16
Bernadette and Wolowitz leave their kids for the first time; Penny and Leonard try to keep a secret; Sheldon and Amy stick together; and Koothrappali makes a new friend, as the gang travels together into an uncharted future.
23	The Change Constant	2019-05-16
Sheldon and Amy await big news.
22	The Maternal Conclusion	2019-05-09
Leonard is pleasantly surprised when Beverly comes to visit and she's genuinely kind to him, until he finds out the real reason she's there. Also, Denise and Stuart overstay their welcome at the Wolowitz house.
21	The Plagiarism Schism	2019-05-02
Kripke has proof that Dr. Pemberton plagiarized his thesis in college, and Sheldon and Amy aren't sure if they should turn him in or not. Also, Wolowitz is happily surprised to learn that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him back in the day.
20	The Decision Reverberation	2019-04-25
Koothrappali is worried people won't take him seriously in his own field after publishing a paper that suggests he may have discovered alien life. Also, Leonard wants to be the principal investigator on a plasma physics study.
19	The Inspiration Deprivation	2019-04-18
The concept of what it would mean for women everywhere if Amy were to win a Nobel Prize causes Amy to have a meltdown. Also, Koothrappali and Wolowitz try to relive the good old days after Wolowitz buys a scooter that looks like the one he had years ago.
18	The Laureate Accumulation	2019-04-04
When competitors Pemberton and Campbell charm America on a publicity tour, Sheldon and Amy try to bring Nobel laureates Kip Thorne, George Smoot and Frances Arnold to their side. Also, Halley’s fear of the dark leads to opportunity and conflict for Howard, Bernadette and Stuart.
17	The Conference Valuation	2019-03-07
When Penny and Bernadette go to San Diego for a pharmaceutical sales convention, Wolowitz is in charge of the kids. Also, Sheldon finds a book on experimenting on kids, and the guys plus Amy make a day of it.
16	The D & D Vortex	2019-02-21
The gang finds out Wil Wheaton hosts a celebrity Dungeons and Dragons game involving William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith. Deception and betrayal are the path to make it to the one open seat.
15	The Donation Oscillation	2019-02-07
Penny tries to seduce an abstaining Leonard to ruin his "donation" for her ex-boyfriend, Zack, and his wife, Marissa. Also, Wolowitz, Bernadette, Anu and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip.
14	The Meteorite Manifestation	2019-01-31
Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law. Also, Leonard is disappointed when his friends exclude him from a scientific project.
13	The Confirmation Polarization	2019-01-17
Sheldon and Amy's super asymmetry theory is proven by two physicists, Dr. Pemberton and Dr. Campbell from Chicago, who then try to kick Amy off the Nobel nomination. Also, Bernadette has a big success at work and Penny's going to be a part of it—whether she wants to be or not. Guest stars: Caleb Pierce, Joshua Malina, Kal Penn, Sean Astin
12	The Propagation Proposition	2019-01-10
Penny's ex-boyfriend, Zack, and his wife want a baby, but when Zack is infertile, they ask Leonard for help. Also, Koothrappali attempts to mend things with his ex-fiancÃ©e, Anu. Guest stars: Brian George, Brian Thomas Smith, Chip Chinery, Lindsey Kraft, Rati Gupta, Shay Ali
11	The Paintball Scattering	2019-01-03
Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Koothrappali catches Anu with her ex-boyfriend, and Stuart doesn’t want to move in with Denise. Guest stars: Hira Ambrosino, Joshua Malina, Kevin Sussman, Lauren Lapkus, Rati Gupta
10	The VCR Illumination	2018-12-06
Sheldon and Amy are still down about their theory being disproven, but a VHS tape from Sheldon’s past inspires him not to give up. Also, Bernadette turns into a pageant mom when she tries to help Wolowitz ace his Magic Castle audition. Guest stars: Christine Baranski, Iain Armitage, Kurt Scholler, Lance Barber, Montana Jordan
9	The Citation Negation	2018-11-15
Sheldon and Amy are devastated after learning from a Russian paper that Super Asymmetry has already been discovered and disproven. Also, ultra-competitive Bernadette asks Stuart’s girlfriend, Denise, to teach her how to beat Howard in a popular videogame. Guest stars: Lauren Lapkus
8	The Consummation Deviation	2018-11-08
Sheldon tries to bond with Amy’s father, but when Wolowitz lures Mr. Fowler away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler. Also, Koothrappali and Anu try to get physical for the first time. Guest stars: Kathy Bates, Kevin Sussman, Rati Gupta, Teller
7	The Grant Allocation Derivation	2018-11-01
Leonard is caught between a rock and a hard place when he’s responsible for distributing extra grant money. Also, Bernadette turns the backyard playhouse into a hideaway from her husband and kids. Guest stars: John Ross Bowie, Joshua Malina, Maribeth Monroe
6	The Imitation Perturbation	2018-10-25
When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny’s Halloween party. Also, Leonard is shocked that Penny doesn’t remember their first kiss. Guest stars: Brian Posehn, David Theune, Kevin Sussman, Pamela Adlon, Rati Gupta
5	The Planetarium Collision	2018-10-18
When Amy doesn’t have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she’s available to work with him even it if means accidentally sabotaging her career in the process. Also, Koothrappali doesn’t want Wolowitz to join him in hosting a show at the planetarium. Guest stars: Alison Martin, Bob Newhart, Eddie Shin, Hermie Castillo, Joshua Malina
4	The Tam Turbulence	2018-10-11
When Sheldon won’t tell anyone why he’s never mentioned Tam, his childhood best friend, Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj’s fiancÃ©e, Anu, for dinner to get the skinny on her. Guest stars: Jerry O'Connell, Rati Gupta, Robert Wu
3	The Procreation Calculation	2018-10-04
The Wolowitzes’ life gets complicated when Stuart starts bringing his new girlfriend home. Also, Penny and Leonard talk about starting a family while Koothrappali explores an arranged marriage. Guest stars: Keith Carradine, Kevin Sussman, Lauren Lapkus, Matt Knudsen, Rati Gupta
2	The Wedding Gift Wormhole	2018-09-27
Sheldon and Amy drive themselves crazy trying to figure out what “perfect gift” Leonard and Penny gave them for their wedding. Also, Koothrappali decides he wants to settle down and asks his father to arrange a marriage for him. Guest stars: Brian George, Brian Posehn, Kevin Sussman, Kikey Castillo, Lauren Lapkus, Luis Aldana
1	The Conjugal Configuration	2018-09-24
Sheldon and Amy’s honeymoon runs aground in New York, while Penny and Leonard discover they are uncomfortably similar to Amy’s parents, Mr. and Mrs. Fowler. Also, Koothrappali insults physicist Neil deGrasse Tyson and starts a Twitter war. Guest stars: Andy Kim, Bill Nye, Ciara Renee, Giovanni Bejarano, Kathy Bates, Neil deGrasse Tyson, Teller

Season 11 (show/hide)
24	The Bow Tie Asymmetry	2018-05-10
When Amy’s parents and Sheldon’s family arrive for the wedding, everybody is focused on making sure all goes according to plan – everyone except the bride and groom. Guest stars: Brian Posehn, Courtney Henggeler, Jerry O'Connell, John Ross Bowie, Kathy Bates, Kevin Sussman, Lauren Lapkus, Laurie Metcalf, Mark Hamill, Teller, Wil Wheaton
23	The Sibling Realignment	2018-05-03
When Sheldon learns that his mother won’t attend his wedding unless he invites his brother, Georgie, he and Leonard travel to Texas to end a family feud. Also, the Wolowitz kids inadvertently infects Amy, Bernadette, Wolowitz and Koothrappali with pinkeye. Guest stars: Ellie Reed, Jerry O'Connell, Lynn Andrews
22	The Monetary Insufficiency	2018-04-26
Sheldon goes to Vegas to win money for science. Also, Penny and Bernadette take Amy wedding dress shopping, but her terrible choice entangles them in a web of lies. Guest stars: D&#39;Kia Anderson, Evan Charest, Joshua Malina, Kevin Sussman, Mark Berry, Seth Coltan
21	The Comet Polarization	2018-04-19
Sheldon’s comic book store experiences changes when writer Neil Gaiman puts Stuart’s store on the map. Also, Koothrappali takes credit for Penny’s astronomical discovery, and friendships are threatened. Guest stars: Kevin Sussman, Lauren Lapkus, Neil Gaiman, Patrick Daniel
20	The Reclusive Potential	2018-04-12
Sheldon takes the guys to a cabin in the middle of nowhere to meet a reclusive scientist; Penny and Bernadette improvise Amy's bachelorette party. Guest stars: Edward James Gage, James Maslow, Peter MacNicol
19	The Tenant Disassociation	2018-04-05
When Leonard learns Sheldon is the president of the tenants association, he decides to run against him. Also, Bernadette encourages Wolowitz and Koothrappali to find the owner of a drone after they find it in the backyard. Guest stars: Bob Stephenson, Kevin Sussman, Megan McGown, Michelle Arthur, Parvesh Cheena
18	The Gates Excitation	2018-03-29
Penny gets the opportunity to host Bill Gates at work when his company wants to partner with her pharmaceutical company. Also, Leonard, Koothrappali and Wolowitz do everything in their power to meet him, while Sheldon thinks he is the victim of an April Fools prank. Guest stars: Bill Gates, Eileen Galindo, Kevin Sussman, Laura Ceron
17	The Athenaeum Allocation	2018-03-08
Leonard jumps through hoops to help secure the perfect wedding venue for Sheldon and Amy. Also, Bernadette and Wolowitz have a hard time deciding who should stay at home with the kids and who should go back to work. Guest stars: Caleb Pierce, John Ross Bowie, Rachna Khatau
16	The Neonatal Nomenclature	2018-03-01
When Bernadette won't go into labor, all her friends try different tactics to get things started. Also, Wolowitz confronts Bernadette after Amy accidentally reveals she's already chosen their son's name.
15	The Novelization Correlation	2018-02-01
When Sheldon petitions Wil Wheaton to appear on the new Professor Proton show, Wil offers a role to Amy instead. Also, Penny gets angry when she thinks the female protagonist in Leonard's novel is based on her. Guest stars: Christine Baranski, Kevin Sussman, Wil Wheaton
14	The Separation Triangulation	2018-01-18
Koothrappali finds himself in the middle of domestic drama when he learns the woman he's dating, Nell, has a very upset husband, Oliver. Also, when Sheldon rents his old room back for a quiet place to work, he drives Leonard crazy by being a model tenant. Guest stars: Beth Behrs, Walton Goggins
13	The Solo Oscillation	2018-01-11
When Sheldon kicks Amy out to work solo, she and Leonard bond during a series of science experiments. Also, Bert the geologist replaces Wolowitz in the band Footprints on the Moon, and Sheldon finds Penny a surprising source of scientific inspiration. Guest stars: Brian Posehn, Laurie Metcalf, Pamela Adlon
12	The Matrimonial Metric	2018-01-04
To discover who would be most qualified to be best man and maid of honor at their wedding, Sheldon and Amy subject their friends to a series of secret experiments. Also, Penny reveals her true feelings about Amy. Guest stars: Kevin Sussman
11	The Celebration Reverberation	2017-12-14
Sheldon and Wolowitz plan birthday celebrations for Amy and Halley, respectively. Also, Leonard receives a Christmas letter from his brother that causes him to spiral out about his own lack of accomplishments. Guest stars: Kevin Sussman, Pamela Adlon
10	The Confidence Erosion	2017-12-07
Sheldon and Amy try to eliminate stress from wedding planning by applying math to the process. Koothrappali “breaks up” with Wolowitz after realizing his best friend is actually hurting his confidence. Guest stars: Brian George, Brooke Baumer, Kevin Sussman, Marissa Cuevas, Nicole Butler
9	The Bitcoin Entanglement	2017-11-30
Sheldon tries to teach the guys a lesson after they cut him out of a potentially valuable Bitcoin investment. Also, a seven-year-old video reveals a secret about Leonard and Penny's relationship. Guest stars: Brian Thomas Smith, Kevin Sussman
8	The Tesla Recoil	2017-11-16
Leonard and Wolowitz are furious after they learn Sheldon went to work with the military behind their backs. Also, while Bernadette is on bed rest, she asks Raj to do some digging when she suspects Ruchi is trying to steal her job. Guest stars: Dean Norris, John Ross Bowie, Swati Kapila
7	The Geology Methodology	2017-11-09
Sheldon and Bert collaborate on a research project, despite Sheldon's embarrassment. Also, Penny and Bernadette coach Koothrappali on how to navigate his relationship with Ruchi. Guest stars: Brian Posehn, Elka Rodriguez, Kevin Sussman, Swati Kapila
6	The Proton Regeneration	2017-11-02
Sheldon goes head-to-head with Wil Wheaton for the role of the new Professor Proton. Also, Penny steps in to take care of Halley when Bernadette and Wolowitz both wind up on bed rest. Guest stars: Bob Newhart, Cat Hammons, Pamela Adlon, Wil Wheaton
5	The Collaboration Contamination	2017-10-23
Sheldon and Koothrappali confide in Bernadette when they can't handle Amy and Wolowitz working together. Also, Penny and Leonard learn new tactics for how to deal Sheldon from an unlikely source. Guest stars: Efrain Gomez
4	The Explosion Implosion	2017-10-16
Wolowitz and Sheldon bond when they drive to the desert to shoot off a model rocket. Also, when Leonard's mom, Beverly, finds a new best friend in Penny, it rubs Leonard the wrong way. Guest stars: Christine Baranski, Dana L. Wilson, Michael Patrick McGill
3	The Relaxation Integration	2017-10-09
As Sheldon stresses about picking a wedding date, Amy tries to convince him he has a more laid-back side. Also, Koothrappali and Stuart compete to win the heart of Bernadette's new coworker, Ruchi. Guest stars: Kevin Sussman, Swati Kapila
2	The Retraction Reaction	2017-10-02
Leonard angers the university - and the entire physics community - after he gives an embarrassing interview. Also, Amy and Bernadette bond over having to hide their success from Sheldon and Howard. Guest stars: Ira Flatow, Regina King
1	The Proposal Proposal	2017-09-25
Amy enthusiastically accepts Sheldon's marriage proposal. However, when dining with Amy's colleagues later that night, Sheldon is offended that they are more impressed with Amy's work than his own. With help from Stephen Hawking, Sheldon later comes to grips with the fact that he will not always be the center of attention in the marriage. Bernadette is shocked to realize that she is pregnant again. She and Howard are not thrilled at the idea of having another baby so soon after their first. They attempt to convince Leonard and Penny to have a child as well, but are rebuffed. Guest stars: George Wyner, Kevin Sussman, Laurie Metcalf, Riki Lindhome, Stephen Hawking, Susan Chuang

Season 10 (show/hide)
24	The Long Distance Dissonance	2017-05-11
The gang is concerned when Sheldon’s former admirer, Dr. Ramona Nowitzki, resurfaces while Amy is away at Princeton. Guest stars: Kevin Sussman, Riki Lindhome
23	The Gyroscopic Collapse	2017-05-04
Amy is offered a Fellowship at Princeton, Raj makes new living arrangements, and the gyroscope project is spinning out of control! Guest stars: Dean Norris, Kimberly Brooks (III)
22	The Cognition Regeneration	2017-04-27
Leonard isn’t thrilled when Penny considers taking a new job offered by her ex-boyfriend, Zack. Guest stars: Brian Thomas Smith
21	The Separation Agitation	2017-04-13
Howard and Bernadette have a hard time leaving Halley in day care when Bernadette returns to work. Also, Bert introduces the gang to his new girlfriend, Rebecca. Guest stars: April Bowlby, Brian Posehn, Kevin Sussman
20	The Recollection Dissipation	2017-04-06
Sheldon pushes himself to the limit when he collaborates on projects with Leonard and Wolowitz as well as Amy on the same day. Also, Bernadette is nearing the end of her maternity leave and must return to work. Guest stars: Joel Murray
19	The Collaboration Fluctuation	2017-03-30
Leonard, Penny and Raj adjust to their new living arrangement and Sheldon takes an interest in Amy's work. Guest stars: Doug Morency, Pamela Adlon, Tiffany Daniels
18	The Escape Hatch Identification	2017-03-09
Raj searches for a cheaper living arrangement. Guest stars: Christine Baranski, Kevin Sussman
17	The Comic-Con Conundrum	2017-02-23
The guys' annual trip to Comic Con is in doubt when Raj can't afford to go. Guest stars: Kevin Sussman, Pamela Adlon
16	The Allowance Evaporation	2017-02-16
Sheldon and Amy have their first fight since moving in together and Koothrappali is shocked at the realities of financial independence when he stops receiving support from his father. Guest stars: Brian George, Brian Posehn
15	The Locomotion Reverberation	2017-02-09
Leonard and Wolowitz try to distract Sheldon when he slows the progress of their guidance system. Also, Penny and Amy take Bernadette out for the night, leaving Raj and Stuart to care for baby Halley. Guest stars: Dean Norris, Kevin Sussman, Pamela Adlon
14	The Emotion Detection Automation	2017-02-02
Sheldon beta-tests an MIT invention after hearing it can help him read people's emotions. Also, Leonard can't hide his feelings when Penny announces her brother is coming to town, and Raj invites his ex-girlfriends over to give him dating advice. Guest stars: Alessandra Torresani, Kate Micucci, Katie Leclerc, Laura Spencer
13	The Romance Recalibration	2017-01-19
When Penny feels that Leonard is taking her for granted, she decides to go on a spa weekend with Amy. Also, Wolowitz and Koothrappali try to fix a squeaky floorboard in the baby's room.
12	The Holiday Summation	2017-01-05
Sheldon and Amy visit Leonard and Penny for the first time since the holidays and share details about their terrible trip to Texas. Guest stars: Kevin Sussman, Laurie Metcalf, Pamela Adlon
11	The Birthday Synchronicity	2016-12-15
Amy's desire to have an intimate night with Sheldon on her birthday is interrupted by Bernadette going into labor. Guest stars: Kevin Sussman, Pamela Adlon, Vernee Watson
10	The Property Division Collision	2016-12-01
Sheldon and Leonard must divide up their possessions and remove Penny's things from 4B. Guest stars: Christopher Lloyd, Kevin Sussman
9	The Geology Elevation	2016-11-17
When Bert, a Caltech geologist, wins the MacArthur Genius fellowship, Sheldon is overcome with jealousy. Also, Wolowitz finds an old remote control Stephen Hawking action figure he invented. Guest stars: Brian Posehn, John Ross Bowie, Kunal Dudheker, Stephen Hawking
8	The Brain Bowl Incubation	2016-11-10
After a successful experiment combining their genes, Sheldon will stop at nothing to convince Amy they should procreate. Also, Koothrappali is embarrassed to tell the gang what the new woman he’s dating does for a living. Guest stars: Maria Canals-Barrera
7	The Veracity Elasticity	2016-11-03
In order to continue living with Sheldon, Amy lies to him about repairs being made to her apartment and they host an "on location" episode of "Fun With Flags" in Penny’s apartment. Also, Leonard lets Penny decorate Sheldon’s old room after he learns that she has been secretly moving Leonard’s collectibles into storage.
6	The Fetal Kick Catalyst	2016-10-27
Penny is surprised to learn she has fans of her performance in "Serial Ape-ist" when she attends Van Nuys Comic Con with Leonard. Also, Amy hosts a Sheldon-style brunch at Penny’s apartment, and Wolowitz makes an impulsive purchase when he starts stressing out about the baby on the way. Guest stars: Brian Posehn, Bryan Safi, Jareb Dauplaise, Joshua Banday, Kevin Sussman, Michelle Arthur, Tucker Albrizzi
5	The Hot Tub Contamination	2016-10-17
Leonard and Penny must separate a quarreling Sheldon and Amy when their cohabitation does not go as planned, and Sheldon threatens to break off their relationship when Amy refuses to adhere to the bathroom schedule. Also, Howard and Bernadette find unexpected guests at their house when they decide to stay home from a planned vacation. Guest stars: Kevin Sussman
4	The Cohabitation Experimentation	2016-10-10
When Amy's apartment floods, she proposes a "cohabitation experiment" with Sheldon. Also, Howard and Bernadette are upset when Koothrappali learns the gender of the baby before they do.
3	The Dependence Transcendence	2016-10-03
Sheldon can't keep up with the late nights Howard and Leonard are putting in, Raj spends the day with a pregnant Bernadette and Penny and Amy attend a faculty party. Guest stars: Brandon Jones, Brian George, Brian Posehn, Dean Norris
2	The Military Miniaturization	2016-09-26
The Air Force shows interest in the guidance system and Penny lets it slip at work that Bernadette is expecting. Guest stars: Dean Norris, Josh Zuckerman
1	The Conjugal Conjecture	2016-09-19
After Leonard's father, Alfred and Sheldon's mother, Mary share an evening together, everyone deals with an awkward morning the following day. Also, Penny's family arrives for the ceremony, including her anxiety-ridden mother, Susan, and her drug dealing brother, Randall. Guest stars: Christine Baranski, Dean Norris, Jack McBrayer, Judd Hirsch, Katey Sagal, Keith Carradine, Laurie Metcalf

Season 9 (show/hide)
24	The Convergence Convergence	2016-05-12
Leonard and Penny get remarried in front of their friends (who show up), Leonard's parents, Beverly and Alfred (Judd Hirsch) and Sheldon's mother, Mary, who finds something in common with Alfred. Howard gets an unknown email from the Air Force about his invention. Guest stars: Christine Baranski, Judd Hirsch, Laurie Metcalf
23	The Line Substitution Solution	2016-05-05
Sheldon hires Stuart to spend the day with Amy when he’d rather go to a movie screening. Also, Leonard’s mother, Beverly, comes to town and Penny struggles to make a connection with her. Guest stars: Christine Baranski, Kevin Sussman
22	The Fermentation Bifurcation	2016-04-28
Sheldon and Bernadette spend a night together while the rest of the gang goes to a wine tasting party, but things get uncomfortable for Raj when Zack also attends and takes an interest in Claire. Guest stars: Alessandra Torresani, Brian Smith
21	The Viewing Party Combustion	2016-04-21
Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together. Guest stars: Kevin Sussman
20	The Big Bear Precipitation	2016-04-07
Secrets are revealed when Amy and Sheldon join Penny and Leonard on a weekend cabin trip. Raj is more excited about Howard's and Bernadette's impending parenthood than they are. Guest stars: Paralely slzavÃ½ch údolí
19	The Solder Excursion Diversion	2016-03-31
Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Koothrappali sells out Leonard and Wolowitz after they lie to their wives in order to attend an early screening of a movie. Guest stars: H. Michael Croner
18	The Application Deterioration	2016-03-10
Sheldon works up a contract to split their portion of their guidance system invention royalties, but Bernadette does not like how it's done. Raj must again decide between Emily and Claire when they both contact him. Guest stars: Alessandra Torresani, Jim Holmes, Laura Spencer
17	The Celebration Experimentation	2016-02-25
After more than nine years together, the gang finally celebrates Sheldon’s birthday, surprising him with a special guest. Guest stars: Adam West, Christine Baranski, John Ross Bowie, Kevin Sussman, Sara Gilbert, Wil Wheaton
16	The Positive Negative Reaction	2016-02-18
When the gang finds out about Bernadette's pregnancy, they celebrate by singing karaoke. Also, Bernadette is concerned when Wolowitz freaks out over her pregnancy announcement, and Wolowitz is convinced he must make more money to provide for a baby.
15	The Valentino Submergence	2016-02-11
Sheldon and Amy host a live Valentine's Day episode of Fun with Flags, Leonard and Penny grapple with getting older, Howard and Bernadette find a surprise in their hot tub and Raj is torn between Emily and the cute girl he met at the Comic Bookstore. Guest stars: Alessandra Torresani, Creagen Dow, John Ross Bowie, Laura Spencer, Shane Blades
14	The Meemaw Materialization	2016-02-04
Sheldon is thrilled when his Meemaw comes to visit, but his excitement quickly fades when she butts heads with Amy. Also, Raj meets a new girl at the comic book store who makes him question his relationship with Emily. Guest stars: Alessandra Torresani, June Squibb
13	The Empathy Optimization	2016-01-14
The gang decides to head to Vegas for the week on a party bus. Sheldon learns about the importance of empathy and saying sorry. Guest stars: Kevin Sussman, Laura Spencer
12	The Sales Call Sublimation	2016-01-07
Leonard visits a psychiatrist so Penny can make a sales call. Stuart moves out of the Wolowitz house. Sheldon works with Raj looking for extra-solar planets. Guest stars: Jane Kaczmarek, Kevin Sussman
11	The Opening Night Excitation	2015-12-17
As the guys prepare to go to the premiere of the new Star Wars movie, Sheldon plans a special event for Amy's birthday. Guest stars: Bob Newhart, Jeff Witzke, Kevin Sussman, Wil Wheaton
10	The Earworm Reverberation	2015-12-10
Sheldon has a revelation when he realizes why a song was stuck in his head. Also, Amy invites Dave over for dinner despite their previously awkward date, and Wolowitz and Koothrappali become obsessed with a fan of their band, "Footprints on the Moon". Guest stars: Stephen Merchant, Yoshi Barrigas
9	The Platonic Permutation	2015-11-19
It’s Thanksgiving. Sheldon and Amy go on a lunch date to the aquarium as friends. Howard, Bernadette, Raj and Emily help out at a soup kitchen. Leonard and Penny make their first Thanksgiving dinner as a married couple. Guest stars: Elon Musk, Laura Spencer, Wayne Wilderson
8	The Mystery Date Observation	2015-11-12
Amy has a formal date which Leonard, Penny and Bernadette secretly spy on. Sheldon has Howard and Raj help him find a new girlfriend since they found Amy for him. Guest stars: Analeigh Tipton, Stephen Merchant
7	The Spock Resonance	2015-11-05
Adam Nimoy, friend of Wil Wheaton and son of Leonard Nimoy, interviews Sheldon for a Star Trek documentary. Sheldon gets off topic and ends up revealing an engagement ring and his plan to propose to Amy. Bernadette wants to start renovating the house and the issue of starting a family with Howard is brought up. Guest stars: Adam Nimoy, Casey Sander, Stephen Merchant, Wil Wheaton
6	The Helium Insufficiency	2015-10-26
In the midst of a nation-wide helium shortage, Sheldon and Leonard take desperate measures to get the supplies they need. Also, Penny and Bernadette download a dating app on Amy's phone to try and find her a new man. Guest stars: Elena Campbell-Martinez, John Ross Bowie, Kevin Sussman, Michael Rapaport
5	The Perspiration Implementation	2015-10-19
The guys take a fencing lesson from Barry Kripke and Sheldon finds himself in an awkward position when Kripke expresses interest in Amy. Also, when Stuart struggles to get female customers at the Comic Book Store, Penny, Amy and Bernadette come by to help him out. Guest stars: John Ross Bowie, Kevin Sussman, Megan Heyn, Patrika Darbo, Rebecca Ann Johnson
4	The 2003 Approximation	2015-10-12
Leonard and Penny finally move in together leaving Sheldon very upset with this big change in his life and wishing he could go back to a time when he had no emotions in 2003 before he met Leonard. Raj, Howard and Stuart attempt to form a band. Guest stars: Arshad Aslam, Craig Welzbacher, Kevin Sussman, Kurt Koehler, Laura Spencer
3	The Bachelor Party Corrosion	2015-10-05
The guys’ science skills are put to the test when they get a flat tire during Leonard’s bachelor party weekend in Mexico. Also, the girls force Penny to finally tell her family that she eloped with Leonard. Guest stars: Keith Carradine
2	The Separation Oscillation	2015-09-28
Leonard confronts the woman he kissed on the North Sea in an attempt to set Penny’s mind at ease. Also, Sheldon films a special episode of “Fun with Flags” after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny. Guest stars: Melissa Tang
1	The Matrimonial Momentum	2015-09-21
Sheldon is confronted by a mystery of the universe he cannot unravel: when a woman wants time apart to think, exactly how much time does that mean, and is there any way to hurry the process along? In Las Vegas, Penny and Leonard march closer to marching down the aisle, but has Penny gotten over Leonard’s infidelity? And if so, will he do anything to un-get her over it? Guest stars: Jim Meskimen, Laurie Metcalf, Louise Claps

Season 8 (show/hide)
24	The Commitment Determination	2015-05-07
Sheldon pushes Leonard and Penny to choose a date for their wedding and deals with dramatic changes in his own relationship with Amy. Guest stars: Laura Spencer
23	The Maternal Combustion	2015-04-30
Personalities collide when Sheldon and Leonard’s mothers finally meet. Meanwhile, Howard finally decides to “man up” and do his fair share of the housework – but not without a little help from his friends. Guest stars: Christine Baranski, Laurie Metcalf
22	The Graduation Transmission	2015-04-23
Wolowitz questions his engineering abilities when he and Sheldon can’t get a toy drone to fly. Meanwhile, a cancelled flight nearly prevents Leonard from giving the commencement address at his former high school, and Raj pits his parents against each other when his father cuts him off financially. Guest stars: Alice Amter, Brian George
21	The Communication Deterioration	2015-04-16
When Raj is asked to create a message in case a NASA mission discovers alien life, the guys fight over what he should do. Also, Penny is torn between auditioning for a movie or keeping her successful pharmaceutical sales job. Guest stars: Kelli Goss, Sara Erikson
20	The Fortification Implementation	2015-04-09
When Sheldon and Amy build a blanket fort, they come to major crossroads in their relationship. Also, Wolowitz meets the half-brother he never knew he had, and when Penny is invited to appear on Wil Wheaton’s podcast, she and Leonard have a huge, on-air argument. Guest stars: Kevin Smith, Matt Bennett, Rena Strober
19	The Skywalker Incursion	2015-04-02
When Leonard and Sheldon are invited to speak at UC Berkeley, they take a detour to try to meet an idol. Also, when Bernadette and Howard battle over the fate of his Doctor Who TARDIS, Raj and Amy offer to settle the dispute with a game of ping pong. Guest stars: Mark Barrett, Michael Dempsey, Tate Ellington
18	The Leftover Thermalization	2015-03-12
Friction ensues when a magazine fails to mention Leonard in an article about the paper he co-wrote with Sheldon. Also, a blackout at Mrs. Wolowitz’s home leads to a final family dinner in her honor. Guest stars: Kevin Sussman
17	The Colonization Application	2015-03-05
Trouble arises when Amy learns Sheldon has applied for a one-way mission to colonize Mars. Also, a trip to the pet store ends in a fight for Sheldon and Amy, Leonard surprises Penny with a very “adult” purchase, and Raj is caught snooping in Emily’s apartment. Guest stars: Laura Spencer
16	The Intimacy Acceleration	2015-02-26
As a joke, Sheldon and Penny try an experiment designed to make participants fall in love. Also, Leonard, Amy, Raj and Emily spend the evening trying to escape a room with a “zombie.” And, after returning from Mrs. Wolowitz’ funeral, Bernadette and Howard run into trouble at the airport. Guest stars: Laura Spencer, Max Adler, Molly Morgan, Stephanie Escajeda
15	The Comic Book Store Regeneration	2015-02-19
Wolowitz receives some shocking news as everyone prepares for the reopening of Stuart’s comic book store. Penny teaches Sheldon how to “let it go,” but can’t follow her own advice after she learns something infuriating about Amy. Also, Leonard and Raj think they spot Nathan Fillion at a restaurant. Guest stars: Angela Relucio, John Ross Bowie, Nathan Fillion
14	The Troll Manifestation	2015-02-05
Leonard and Sheldon publish a paper which is widely accepted except for comments from an internet troll. Meanwhile, the girls reminisce about embarassing incidents from their past. Guest stars: Jim Meskimen, Stephen Hawking
13	The Anxiety Optimization	2015-01-29
The gang tries to help Sheldon when he becomes stuck in a rut at work by increasing his anxiety level. Howard teases Raj with a new game called "Cinnamon or Emily?" Guest stars: Ed Lieberman, Laura Spencer
12	The Space Probe Disintegration	2014-12-18
Wolowitz tries to distract Raj, who is anxiously awaiting data from a space probe he helped launch. Meanwhile, Sheldon and Leonard go dress shopping with Penny and Amy.
11	The Clean Room Infiltration	2014-12-11
Leonard and Howard turn to Raj for help in dealing with a work emergency when they nearly come to blows after blaming each other for a potential disaster at the university. Amy throws an authentic Victorian Christmas party, while Sheldon seeks revenge on her for making him celebrate the holidays. Guest stars: Brian George, Dakin Matthews, Michael Reetz
10	The Champagne Reflection	2014-11-20
While Sheldon says a tearful goodbye to the final instalment of "Fun with Flags", Leonard, Howard and Raj search for something significant in a dead professor's research. And Bernadette is shocked to learn of her co-workers’ true feelings from Penny. Guest stars: John Ross Bowie, LeVar Burton, Paul Wilson, Stephen Root
9	The Septum Deviation	2014-11-13
When Leonard gets minor surgery on his nose, Sheldon is the one in need of sympathy. Meanwhile, Raj's parents' impending divorce causes Howard and Bernadette to work on their own marriage.
8	The Prom Equivalency	2014-11-06
When the gang recreates a high-school prom night on the roof of the guys'; apartment building, Sheldon feels pressure to participate in all the typical romantic traditions. Guest stars: Kara Luiz, Kevin Sussman, Laura Spencer
7	The Misinterpretation Agitation	2014-10-30
The guys try to help Penny out of an awkward work dilemma, when a smitten doctor shows up at her door after her flirtatious sales techniques work a little too well. Meanwhile, Amy and Bernadette argue over whether or not female scientists should play up their sexuality. Guest stars: Billy Bob Thornton
6	The Expedition Approximation	2014-10-20
Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel deep underground. Leonard and Penny seek advice from Howard and Bernadette after they fight about money.
5	The Focus Attenuation	2014-10-13
During their weekend in Las Vegas, Bernadette and Amy accuse Penny of being a buzz kill; the guys try to invent the next big thing.
4	The Hook-Up Reverberation	2014-10-06
Raj's honesty comes back to haunt him when his new girlfriend is unfriendly to Penny; the guys think about becoming part owners in Stuart's store. Guest stars: Laura Spencer
3	The First Pitch Insufficiency	2014-09-29
Wolowitz feels nervous when he is asked to throw the first pitch at a Los Angeles Angels game; Penny and Leonard want to prove Sheldon wrong after he says he and Amy are the better couple. Guest stars: Mike Massimino
2	The Junior Professor Solution	2014-09-22
When Sheldon must teach a class, Howard decides to take it; Amy takes advantage of the tension between Penny and Bernadette. Guest stars: Regina King
1	The Locomotion Interruption	2014-09-22
Leonard and Amy make an unexpected trip to Arizona to fetch Sheldon; Penny interviews for a job at Bernadette's company; Stuart's relationship with Mrs. Wolowitz disturbs Howard. Guest stars: Stephen Root

Season 7 (show/hide)
24	The Status Quo Combustion	2014-05-15
Faced with an uncertain future, Sheldon considers a major change; Emily and Raj decide to take things to the next level. Guest stars: Carol Ann Susi, Christine Baranski, Kevin Sussman, Monica Garcia
23	The Gorilla Dissolution	2014-05-08
A bad day compels Penny to re-evaluate her choices -- including Leonard; Bernadette and Howard must care for Mrs. Wolowitz; Sheldon gives Raj advice on relationships. Guest stars: Carol Ann Susi, Casper Smart, Kaliko Kauahi, Laura Spencer, Steve Valentine, Wil Wheaton
22	The Proton Transmogrification	2014-05-01
Professor Proton helps Sheldon deal with grief; Leonard gets into a competition with Penny; Bernadette and Amy prepare a "Star Wars Day" gift for the guys. Guest stars: Bob Newhart
21	The Anything Can Happen Recurrence	2014-04-24
Sheldon gives spontaneity a try, which causes unexpected friction for Penny, Bernadette and Amy; Raj asks Howard for help with preparation for a date with Emily. Guest stars: Carol Ann Susi, Kimberly Hebert Gregory, Laura Spencer
20	The Relationship Diremption	2014-04-10
Sheldon has a personal crisis when he decides string theory is a waste of his time; a double date ends in embarrassment for Howard. Guest stars: John Ross Bowie, Laura Spencer, Stephen Hawking
19	The Indecision Amalgamation	2014-04-03
Raj struggles with guilt when he dates two women at once; Penny has a chance to play a part in a cheesy movie; Sheldon is torn between two gaming systems. Guest stars: Fernando Rivera, Laura Spencer, Rod Keller, Wil Wheaton
18	The Mommy Observation	2014-03-13
Sheldon is faced with a new reality when he visits his mom in Houston; a murder mystery party starts arguments. Guest stars: Kevin Sussman, Laurie Metcalf
17	The Friendship Turbulence	2014-03-06
Bernadette tries to negotiate peace between Sheldon and Wolowitz; Penny receives an embarrassing offer; Raj wants Amy to write to a woman on his behalf. Guest stars: Laura Spencer
16	The Table Polarization	2014-02-27
When Leonard buys a dining room table, Sheldon re-evaluates the changes in his life; Bernadette is torn when Wolowitz gets the chance to go back to space. Guest stars: Carol Ann Susi, Casey Sander, Christopher Neiman
15	The Locomotive Manipulation	2014-02-06
Sheldon and Amy go on a trip to wine country with Howard and Bernadette; Penny and Leonard rush Raj's dog to the vet Guest stars: Alex Ball, Eric Petersen, Tania Raymonde
14	The Convention Conundrum	2014-01-30
Unable to get Comic-Con tickets, Sheldon tries to hold his own convention and ends up spending a wild evening with James Earl Jones; the ladies try to act maturely. Guest stars: Carrie Fisher, James Earl Jones
13	The Occupation Recalibration	2014-01-09
Sheldon must learn how to relax when he is forced to take a vacation; Leonard tries to support Penny when she quits her job; Bernadette needs to replace one of Stuart's comic books. Guest stars: Brian Posehn, Ian Scott Rudolph, Josh Peck
12	The Hesitation Ramification	2014-01-02
As Leonard tries to help Penny with a disappointment, Penny asks him a bold question about their relationship; Sheldon wants to learn how to be funny. Guest stars: Lexie Contursi, Marcus Folmar
11	The Cooper Extraction	2013-12-12
While Sheldon is in Texas, the rest of the gang realize how much he has changed their lives as they decorate the apartment Christmas tree. Guest stars: Brian Smith, Carol Ann Susi, Kevin Sussman, Laurie Metcalf
10	The Discovery Dissipation	2013-12-05
Sheldon faces a crisis after Leonard disproves his accidental scientific discovery. Meanwhile, Raj must stay with Howard & Bernadette for a week. Guest stars: Ira Flatow, John Ross Bowie, Wil Wheaton
9	The Thanksgiving Decoupling	2013-11-21
An upset Sheldon protests when the entire gang drags him to Mrs. Wolowitz's house for Thanksgiving. Meanwhile, Penny and Leonard must deal with a mistake from her past. Guest stars: Brian Thomas Smith, Carol Ann Susi, Casey Sander
8	The Itchy Brain Simulation	2013-11-14
Leonard tries to keep Sheldon from overreacting when a past mistake comes to light, but Sheldon punishes Leonard by making him "walk a mile in his shoes." Meanwhile, Penny confronts Raj's ex-girlfriend, Lucy (guest star Kate Micucci). Guest stars: Kate Micucci, Morgan Hewitt
7	The Proton Displacement	2013-11-07
Sheldon feels slighted when Professor Proton (recurring guest star Bob Newhart) seeks advice from Leonard instead of him, and he seeks revenge by befriending a rival science TV host, Bill Nye (guest starring as himself). Meanwhile, Raj gets jealous when Howard crashes "girls' night." Guest stars: Bill Nye, Bob Newhart
6	The Romance Resonance	2013-10-24
Sheldon's latest scientific breakthrough makes him feel like a fraud – and threatens to haunt him forever. Meanwhile, Howard's romantic gesture to Bernadette causes Penny to step up her game with Leonard. Guest stars: Andrew Hill Newman, John Apicella, Nick Ullett, Tom Fonss
5	The Workplace Proximity	2013-10-17
Sheldon must decide how much "Amy time" is too much after she takes a job at his university, and their relationship is put to the test. Meanwhile, Howard finds himself sleeping on Raj's couch after a fight with Bernadette. Guest stars: Ayumi Iizuka, Todd Eric Andrews
4	The Raiders Minimization	2013-10-10
After Amy ruins one of Sheldon's favorite movies – Raiders of the Lost Ark – he gets defensive, seeking revenge. Meanwhile, Leonard discovers a way to get Penny to do anything; and Raj and Stuart create online dating profiles. Guest stars: Christine Baranski, Christine Corpuz, Kevin Sussman
3	The Scavenger Vortex	2013-10-03
When the entire gang competes in a cutthroat scavenger hunt designed by Raj that tests their science knowledge and street smarts, it brings out the best – and worst – in everyone. Guest stars: Kevin Sussman
2	The Deception Verification	2013-09-26
On the second part of the one-hour seventh season premiere, Raj gets consoled about his ex-girlfriend and Howard's relationship with his mother causes an unusual threat to his masculinity. Kevin Sussman returns as Stuart, the comic book store owner. Guest stars: Barak Hardley, Kevin Sussman
1	The Hofstadter Insufficiency	2013-09-26
In the first part of the one-hour seventh season premiere, Sheldon and Penny bond in Leonard's absence, but it's Sheldon's feelings that are crushed when Leonard returns from the North Sea. Guest star Regina King returns as Mrs. Davis, the University's Director of Employee Relations. Guest stars: Aaron Takahashi, Alex Ball, Regina King, Sophie Oda

Season 6 (show/hide)
24	The Bon Voyage Reaction	2013-05-16
When Leonard is considered for an exciting research opportunity, Sheldon becomes jealous and tries to scare him into backing out. Meanwhile, Raj's relationship with Lucy is strained when he tries to get her to meet his friends. Guest stars: Kate Micucci
23	The Love Spell Potential	2013-05-09
Amy and Sheldon's relationship takes a surprising turn during a game of "Dungeons & Dragons"; Lucy and Koothrappali have an awkward date. Guest stars: David Trice, Kate Micucci
22	The Proton Resurgence	2013-05-02
Leonard and Sheldon hire the host (Bob Newhart) of their favorite childhood TV show to perform; Bernadette and Howard run into trouble while dog-sitting for Raj's pet. Guest stars: Bob Newhart, Troy Winbush
21	The Closure Alternative	2013-04-25
Amy tries to help Sheldon get over his compulsive need for closure when one of his favorite TV shows is canceled; Raj discovers a secret about Lucy. Guest stars: Kate Micucci
20	The Tenure Turbulence	2013-04-04
The girls get involved when Leonard, Sheldon and Raj compete for tenure at the University. Guest stars: John Ross Bowie, Regina King
19	The Closet Reconfiguration	2013-03-14
Howard considers whether or not he should open a letter from his father; Penny and Leonard host a "grown-up" cocktail party.
18	The Contractual Obligation Implementation	2013-03-07
Leonard, Sheldon and Wolowitz talk to junior high girls about science-related careers; Raj plans a date with Lucy. Guest stars: Brian Posehn, Dawson Fletcher, Diamond White, Kate Micucci, Piper Mackenzie Harris
17	The Monster Isolation	2013-02-21
After a bad date, Koothrappali decides to never leave his apartment; Penny's acting skills impress Sheldon. Guest stars: Kate Micucci, Kevin Sussman, Riccardo LeBron
16	The Tangible Affection Proof	2013-02-14
The guys search for a perfect Valentine's Day gift for their significant others; Stuart and Raj host a "lonely people" party at the comic book store. Guest stars: Briana Cuoco, Josh Brener, Kate Micucci, Kevin Sussman, Margo Harshman
15	The Spoiler Alert Segmentation	2013-02-07
A fight between Sheldon and Leonard impacts Amy and Penny's living arrangements; while Howard is away, Raj helps Mrs. Wolowitz out. Guest stars: Carol Ann Susi
14	The Cooper/Kripke Inversion	2013-01-31
Sheldon faces a crisis of confidence when he is forced to work with his nemesis, Barry Kripke; Raj and Howard buy expensive action figures of themselves. Guest stars: John Ross Bowie
13	The Bakersfield Expedition	2013-01-10
As the guys don costumes and go on a road trip to a comic book convention, the ladies decide to stay home and try to interpret a comic book. Guest stars: Angela Sargeant
12	The Egg Salad Equivalency	2013-01-03
When Sheldon is accused of sexual harassment, he ends up getting Raj, Leonard and Wolowitz in trouble. Guest stars: Margo Harshman, Regina King
11	The Santa Simulation	2012-12-13
During a game, Sheldon revisits Christmas memories; Amy, Penny and Bernadette look for a date for Koothrappali. Guest stars: Dakin Matthews
10	The Fish Guts Displacement	2012-12-06
When Amy gets sick, Sheldon tries to nurse her back to health; Wolowitz and his father-in-law plan a fishing trip. Guest stars: Casey Sander, Meagen Fay
9	The Parking Spot Escalation	2012-11-29
Sheldon and Wolowitz's fight over a parking spot at the university impacts the whole gang. Guest stars: William Stanford Davis
8	The 43 Peculiarity	2012-11-15
Raj and Howard try to to figure out why Sheldon disappears at 2:45 every afternoon; jealousy arises in Penny and Leonard's relationship. Guest stars: Margo Harshman, Ryan Cartwright
7	The Habitation Configuration	2012-11-08
Bernadette wants Wolowitz to move out of his mom's house; Sheldon is caught in the middle of Amy and Wil Wheaton's argument. Guest stars: LeVar Burton, Wil Wheaton
6	The Extract Obliteration	2012-11-01
A game threatens Sheldon's relationship with Stephen Hawking; Penny secretly signs up for a college class. Guest stars: Stephen Hawking
5	The Holographic Excitation	2012-10-25
The gang heads to Stuart's comic book store to celebrate Halloween; Leonard uses science to seduce Penny. Guest stars: Buzz Aldrin, Janelle Marra
4	The Re-Entry Minimization	2012-10-18
Wolowitz's return from space isn't all he expected; game night becomes a gender war. Guest stars: Carol Ann Susi, Howie Mandel, Jan Hoag, John Mendoza, Ken Lerner, Michael J. Massimino, Pasha D. Lychnikoff
3	The Higgs Boson Observation	2012-10-11
Amy feels threatened by Sheldon's new assistant; Wolowitz starts to feel the pressures of being in space. Guest stars: Margo Harshman, Pasha D. Lychnikoff
2	The Decoupling Fluctuation	2012-10-04
Sheldon tries to intervene when he learns that Penny is thinking about breaking up with Leonard; Howard is picked on. Guest stars: Mike Massimino, Pasha Lychnikoff
1	The Date Night Variable	2012-09-27
Raj faces his loneliness when his friends are out on dates; while in space, Wolowitz gets drawn into a fight between Bernadette and his mom. Guest stars: Carol Ann Susi, Pasha Lychnikoff

Season 5 (show/hide)
24	The Countdown Reflection	2012-05-10
The fifth season ends with Howard and Bernadette deciding to get married before his NASA mission, causing the gang to scurry into overdrive in an effort to stage the wedding. NASA astronaut Mike Massimino has a cameo as himself. Guest stars: Mike Massimino
23	The Launch Acceleration	2012-05-03
When NASA moves up Howard's mission, he must face his fears and Bernadette's dad, thus putting the wedding plans in jeopardy. Meanwhile, Leonard says something surprising to Penny in the bedroom.
22	The Stag Convergence	2012-04-26
After the guys throw Howard a bachelor party, Bernadette reconsiders marrying him after learning about his sexual history. Guest stars: John Ross Bowie, Kevin Sussman, Wil Wheaton
21	The Hawking Excitation	2012-04-05
When Wolowitz gets to work with Stephen Hawking, Sheldon is willing to do anything to meet his hero. Guest stars: Stephen Hawking
20	The Transporter Malfunction	2012-03-29
Penny buys Leonard and Sheldon “Star Trek” collectibles as a thank-you, leading Sheldon to be haunted by Mr. Spock. Meanwhile, Raj decides he has met the “Future Mrs. Koothrappali” after his parents set him up on a date. Guest stars: Leonard Nimoy
19	The Weekend Vortex	2012-03-08
Sheldon must choose between joining Amy at her aunt's birthday party or playing videogames all weekend with the guys.
18	The Werewolf Transformation	2012-02-23
Sheldon becomes agitated when his regular barber is out sick. Astronaut training causes Howard to reconsider wanting to go into space. Penny beats Leonard in chess, the first time she plays. Guest stars: Peter Onorati, Vernee Watson
17	The Rothman Disintegration	2012-02-16
Sheldon and his rival Barry Kripke fight it out over the availability of a new office. Penny gets a gift from Amy that really tests their friendship and it doesn't end well.
16	The Vacation Solution	2012-02-09
When Sheldon is forced to take his vacation, he goes to work with Amy in her neurobiology lab. Guest stars: Joshua Malina, Nick Clifford
15	The Friendship Contraction	2012-02-02
Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname. Guest stars: Carol Ann Susi, Kevin Sussman, Michael J. Massimino
14	The Beta Test Initiation	2012-01-26
Leonard and Penny deal with the idea of starting a relationship again and Raj finally finds a "woman" he can talk to without being drunk, in the form of Siri on his new phone. Meanwhile, Sheldon decides to start a YouTube series entitled "Sheldon Cooper presents Fun with Flags" with the help of Amy. Guest stars: Becky O'Donohue, John Ross Bowie
13	The Recombination Hypothesis	2012-01-19
Leonard, who broke up with Priya, asks Penny out to a spur-of the-moment romantic dinner for two, and the duo contemplates on their relationship.
12	The Shiny Trinket Maneuver	2012-01-12
Sheldon gets in trouble with Amy when he isn't impressed by her recent accomplishment, and Howard must come to grips with Bernadette's dislike of children.
11	The Speckerman Recurrence	2011-12-08
When Leonard's former high school tormentor resurfaces, Leonard must confront him. Meanwhile, Penny realizes she did her fair share of tormenting in the past.
10	The Flaming Spittoon Acquisition	2011-11-17
Sheldon considers taking his relationship with Amy to the next level when Stuart from the comic book store asks her out on a date. Guest stars: Josh Brener, Kevin Sussman, Mayim Bialik, Melissa Rauch
9	The Ornithophobia Diffusion	2011-11-10
Leonard and Penny try hanging out as friends on a 'non-date,' but end up purposely ruining each others chances with perspective dates. Meanwhile, Sheldon enlists the help of Bernadette and Amy to overcome his fear of birds. Guest stars: Ashley Morris, Blake Berris, Mayim Bialik, Melissa Rauch
8	The Isolation Permutation	2011-11-03
Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her and turns to a reluctant Sheldon for comfort.
7	The Good Guy Fluctuation	2011-10-27
A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween. Guest stars: Aarti Mann, Courtney Ford, Kevin Sussman
6	The Rhinitis Revelation	2011-10-20
Sheldon's mother, Mary Cooper, comes to visit, but Sheldon is annoyed that she also spends time with the rest of the gang, instead of catering to his every demand. Guest stars: Laurie Metcalf
5	The Russian Rocket Reaction	2011-10-13
Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity. Guest stars: Brent Spiner, Wil Wheaton
4	The Wiggly Finger Catalyst	2011-10-06
Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to, but the gang suspects that she may be taking advantage of Raj. Guest stars: Alice Amter, Brian George, Katie Leclerc
3	The Pulled Groin Extrapolation	2011-09-29
Leonard and Amy get to know each other better when Amy invites Leonard to a wedding. Meanwhile, Howard and Bernadette spend the weekend with Mrs. Wolowitz.
2	The Infestation Hypothesis	2011-09-22
A fight between Sheldon and Penny leaves Amy caught in the middle. Meanwhile, Leonard tries to spice up his long-distance relationship with Priya.
1	The Skank Reflex Analysis	2011-09-22
Penny is worried with how damaged her friendship with the guys will be in the aftermath of her sleeping with Raj, while Sheldon becomes the leader of the paintball team.

Season 4 (show/hide)
24	The Roommate Transmogrification	2011-05-19
When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap apartments and Penny does something she regrets.
23	The Engagement Reaction	2011-05-12
When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.
22	The Wildebeest Implementation	2011-05-05
Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.
21	The Agreement Dissection	2011-04-28
When Priya finds a loophole in the roommate agreement to throw Sheldon out for the night, Penny, Amy and Bernadette take him to a nightclub.
20	The Herb Garden Germination	2011-04-07
Sheldon and Amy decide to start several rumors about the others as a test. Meanwhile, Howard takes his relationship with Bernadette to an even higher level.
19	The Zarnecki Incursion	2011-03-31
The guys go all out to help Sheldon find the person responsible for hacking his online gaming account, while the girls' hatred for Priya increases.
18	The Prestidigitation Approximation	2011-03-10
Sheldon is baffled by Wolowitz's magic trick. Meanwhile, Leonard realizes dating Priya may make it impossible to continue being friends with Penny.
17	The Toast Derivation	2011-02-24
Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group. Guest stars: LeVar Burton
16	The Cohabitation Formulation	2011-02-17
As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister Priya. Guest stars: Aarti Mann, Carol Ann Susi
15	The Benefactor Factor	2011-02-10
A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science. Guest stars: Jessica Walter, Joshua Malina
14	The Thespian Catalyst	2011-02-03
Hoping it will make him a better teacher, Sheldon has Penny give him acting lessons. Raj has fantasies about a friend's girlfriend.
13	The Love Car Displacement	2011-01-20
When the gang road trips to a conference, tensions run high when Bernadette runs into her ex-boyfriend. Guest stars: Rick Fox
12	The Bus Pants Utilization	2011-01-06
Leonard's idea for a smartphone app derails his friendship with Sheldon.
11	The Justice League Recombination	2010-12-16
The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.
10	The Alien Parasite Hypothesis	2010-12-09
Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.
9	The Boyfriend Complexity	2010-11-18
Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope. Guest stars: Keith Carradine
8	The 21-Second Excitation	2010-11-11
While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party. Guest stars: Eric Andre, Mayim Bialik, Melissa Rauch, Wil Wheaton
7	The Apology Insufficiency	2010-11-04
Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy. Guest stars: Eliza Dushku
6	The Irish Pub Formulation	2010-10-28
Leonard keeps a romantic affair a secret from Sheldon, Howard and Raj.
5	The Desperation Emanation	2010-10-21
Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.
4	The Hot Troll Deviation	2010-10-14
An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work. Guest stars: George Takei, Katee Sackhoff, Melissa Rauch
3	The Zazzy Substitution	2010-10-07
The guys are concerned as Sheldon searches for an alternative to human companionship. Guest stars: Laurie Metcalf, Mayim Bialik
2	The Cruciferous Vegetable Amplification	2010-09-30
Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span. Guest stars: Steve Wozniak
1	The Robotic Manipulation	2010-09-23
Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm. Guest stars: Mayim Bialik, Vernee Watson-Johnson

Season 3 (show/hide)
23	The Lunar Excitation	2010-05-24
While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online. Guest stars: Mayim Bialik
22	The Staircase Implementation	2010-05-17
Leonard tells Penny about how he met Sheldon for the first time...and what happened to the elevator.
21	The Plimpton Stimulation	2010-05-10
Leonard and Sheldon compete for the attention of a famous female physicist. Guest stars: Judy Greer
20	The Spaghetti Catalyst	2010-05-03
When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy.
19	The Wheaton Recurrence	2010-04-12
A fight between Leonard and Penny threatens their relationship, while Sheldon battles Wil Wheaton in bowling. Guest stars: Wil Wheaton
18	The Pants Alternative	2010-03-22
Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.
17	The Precious Fragmentation	2010-03-08
When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart. Guest stars: Frank Maharajh
16	The Excelsior Acquisition	2010-03-01
Sheldon winds up in traffic court when he gets a ticket because of Penny.
15	The Large Hadron Collision	2010-02-08
Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.
14	The Einstein Approximation	2010-02-01
Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny. Guest stars: Kevin Brief, Melissa Rauch, Yeardley Smith
13	The Bozeman Reaction	2010-01-18
When their apartment is robbed, Leonard and Sheldon turn to their friends to create a state-of-the-art security system. Guest stars: Artie O'Daly, Julio Oscar Mechoso
12	The Psychic Vortex	2010-01-11
Leonard is aghast to find out a secret of Penny's: she believes in psychics. Meanwhile, Sheldon tries to assist Koothrappali in picking up a girl at a university mixer. Guest stars: Danica McKellar, David Trice, Jen Drohan, Melissa Rauch
11	The Maternal Congruence	2009-12-14
A Christmas visit from his mother has Leonard discovering she's kept a lot of news from him that she shares with Sheldon and worrying if she'll approve of his romance with Penny.
10	The Gorilla Experiment	2009-12-07
Penny gets help from Sheldon in order to understand what Leonard's work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.
9	The Vengeance Formulation	2009-11-23
After he's humiliated on National Public Radio, Sheldon vows to destroy Kripke, while Wolowitz tries not to destroy his new relationship with Bernadette. Guest stars: Ira Flatow, Katee Sackhoff
8	The Adhesive Duck Deficiency	2009-11-16
With Leonard, Howard and Raj away camping in the desert, an injured Penny has only Sheldon to rely on.
7	The Guitarist Amplification	2009-11-09
When Penny has an old friend staying over at her apartment, an argument ensues between her and Leonard, causing Sheldon to get caught between the couple.
6	The Cornhusker Vortex	2009-11-02
Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.
5	The Creepy Candy Coating Corollary	2009-10-19
After overhearing that Wil Wheaton is entering a trading-card competition, Sheldon decides to enter it himself. Meanwhile, Penny sets up one of her friends on a date with Wolowitz. Guest stars: Wil Wheaton
4	The Pirate Solution	2009-10-12
Raj must find a new job or be sent back to India, but Sheldon has a solution, which leaves Leonard and Penny dealing with Howard as a third wheel. Guest stars: Elena Campbell-Martinez, Elizabeth Bogush, Oliver Muirhead
3	The Gothowitz Deviation	2009-10-05
Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification. Guest stars: Andy Mackenzie, Molly Morgan, Sarah Buehler
2	The Jiminy Conjecture	2009-09-28
Leonard and Penny struggle to recover from an awkward first hookup while Sheldon and Howard stake their best comic books on a bet to determine the species of a cricket.
1	The Electric Can Opener Fluctuation	2009-09-21
When Sheldon learns the guys tampered with his expedition data he got from the arctic, he returns to Texas in disgrace. This results in the guys following him, which threatens Leonard's hope for some romantic time with Penny and the guys' friendship with Sheldon.

Season 2 (show/hide)
23	The Monopolar Expedition	2009-05-11
The guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.
22	The Classified Materials Turbulence	2009-05-04
Penny's second date with Stuart sees her making a comment that gives Leonard new hope for a relationship with her. Wolowitz realizes there's a crucial error in a NASA project he's working on.
21	The Vegas Renormalization	2009-04-27
Leonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny. Guest stars: Jodi Lyn O'Keefe
20	The Hofstadter Isotope	2009-04-13
When a fellow comic book enthusiast hits on Penny it leads to Leonard and Howard going to a bar's on Ladies' Night.
19	The Dead Hooker Juxtaposition	2009-03-30
Penny squares off with a new beautiful female neighbor who may become the building's "new Penny." Guest stars: Carol Ann Susi, Valerie Azlynn
18	The Work Song Nanocluster	2009-03-16
Penny's home business turns into a complete nightmare when Sheldon takes over.
17	The Terminator Decoupling	2009-03-09
Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress is on board the train they are taking to San Francisco. Guest stars: George Smoot, Summer Glau
16	The Cushion Saturation	2009-03-02
A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.
15	The Maternal Capacitance	2009-02-09
Leonard and Penny are drawn together after a disastrous visit from Leonard's mother. Guest stars: Christine Baranski
14	The Financial Permeability	2009-02-02
Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend. Guest stars: Brian Patrick Wade
13	The Friendship Algorithm	2009-01-19
Sheldon creates a scientific procedure for making friends. Guest stars: Jade Zdanow, Jane Galloway Heitz, John Ross Bowie, Will Deutsch
12	The Killer Robot Instability	2009-01-12
Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for. Guest stars: Carol Ann Susi, John Ross Bowie
11	The Bath Item Gift Hypothesis	2008-12-15
Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette. Guest stars: Michael Hyatt, Michael Trucco
10	The Vartabedian Conundrum	2008-12-08
Leonard asks Penny for advice when his new relationship starts moving too fast. Guest stars: Sara Rue
9	The White Asparagus Triangulation	2008-11-24
Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards. Guest stars: Sara Rue
8	The Lizard-Spock Expansion	2008-11-17
Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life. Guest stars: Carol Ann Susi, Sara Rue
7	The Panty PiÃ±ata Polarization	2008-11-10
When Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate. Meanwhile, Howard and Rajesh try to find the house where all the models from "America's Top Model" are staying. Guest stars: Analeigh Tipton
6	The Cooper-Nowitzki Theorem	2008-11-03
Sheldon and the gang are confused when a young grad student is attracted to him. Guest stars: Emily Happe, Riki Lindhome
5	The Euclid Alternative	2008-10-20
Leonard and his friends stage an intervention to force Sheldon to face his fear of driving. Guest stars: Elena Campbell-Martinez, Livia Trevino, Octavia Spencer
4	The Griffin Equivalency	2008-10-13
Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article. Guest stars: Mark Harelik
3	The Barbarian Sublimation	2008-10-06
Sheldon creates a monster when he introduces Penny to online gaming. Meanwhile, Sheldon disagrees with Leslie Winkle at work. Guest stars: Mark Hames, Mark Harelik, Tyler Olson
2	The Codpiece Topology	2008-09-29
A jealous Leonard reacts to Penny's new guy by rebounding with Leslie Winkle. Guest stars: Travis Schuldt
1	The Bad Fish Paradigm	2008-09-22
Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant. Guest stars: Carol Ann Susi

Season 1 (show/hide)
17	The Tangerine Factor	2008-05-19
Penny's break-up spurs Leonard to summon up the courage to ask her out, and each head to Sheldon for advice on their upcoming date. Guest stars: James Hong
16	The Peanut Reaction	2008-05-12
Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track. Meanwhile, Howard makes a terrible sacrifice for the sake of the surprise. Guest stars: Chuck Carter, Judith Moreland, Ronald Hunter, Vernee Watson-Johnson
15	The Pork Chop Indeterminacy	2008-05-05
The rest of the gang fall for Sheldon's twin sister, and Leonard's plan to win her heart is derailed when Sheldon declares he'll be the one to decide who can date her.
14	The Nerdvana Annihilation	2008-04-28
When the guys buy a time machine prop from a classic 1960 movie, Penny lashes out at Leonard and he decides it's time to give up his habit, much to his friends' protestation. Guest stars: Andrew Walker
13	The Bat Jar Conjecture	2008-04-21
Sheldon finds himself booted from the gang's Physics Bowl team and replaced by Leslie Winkle, so he forms his own team, hoping to prove he's superior. Guest stars: Adam Gregor, Mark Harelik, Sandra Marquez, Sergio Enrique
12	The Jerusalem Duality	2008-04-14
When Sheldon meets a 15-year-old physicist prodigy, he's rattled and threatened and Leonard tries to help him look for ways to debunk his research. Guest stars: Austin Lee, Emma Degerstedt, Joel Brooks, Mark Harelik
11	The Pancake Batter Anomaly	2008-03-31
With his friends knowing how sour he acts when sick—and avoiding him as a result—Sheldon is nursed by Penny, who hasn't a clue what she's in for. Guest stars: Carol Ann Susi, Erin Allin O'Reilly
10	The Loobenfeld Decay	2008-03-24
Leonard and Sheldon each lie to avoid seeing Penny's concert, but Sheldon's lie is a bit too complicated for his own good. Guest stars: DJ Qualls
9	The Cooper-Hofstadter Polarization	2008-03-17
When they're invited to present at a physics conference, Sheldon's reluctance to share the credit leads to a tiff between him and Leonard, and Penny's intervention only exacerbates the situation. Guest stars: Howard Chan, Talbott Chin
8	The Grasshopper Experiment	2007-11-12
Raj's parents set him up on a blind date, but just when he discovers he can talk to his date, she shows interest in Sheldon. Guest stars: Alice Amter, Brian George, Sarayu Rao
7	The Dumpling Paradox	2007-11-05
When Wolowitz seduces one of Penny's friend who then takes over her apartment, Penny sleeps on Leonard and Sheldon's couch. Meanwhile, Penny is recruited to fill in for Howard on the guys' Halo team. Guest stars: Brooke D'Orsay, Carol Ann Susi, James Hong
6	The Middle Earth Paradigm	2007-10-29
Penny hosts a Halloween party, that ends up putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills. Guest stars: Brian Patrick Wade, Cynthia Holloway, Erin Allin O'Reilly, Kimberly Kevon Williams, Rachel Cannon
5	The Hamburger Postulate	2007-10-22
Fearing he's wasting his time on Penny, Leonard ends up making a connection with colleague Leslie Winkle. Guest stars: Sara Gilbert
4	The Luminous Fish Effect	2007-10-15
When Sheldon gets fired and decides to explore life beyond physics, it's up to Leonard to take drastic action to snap his friend out of his funk. Guest stars: Laurie Metcalf, Mark Harelik, Sierra Edwards
3	The Fuzzy Boots Corollary	2007-10-08
When Leonard learns Penny is seeing someone, he decided to asks a nerdy female co-worker out on a date.
2	The Big Bran Hypothesis	2007-10-01
Leonard volunteers to sign for a package in an attempt to make a good impression on Penny, but when he enlists Sheldon for help, his attempt at chivalry goes terribly awry.
1	Pilot	2007-09-24
Brilliant physicist roommates Leonard and Sheldon meet their new neighbor Penny, who begins showing them that as much as they know about science, they know little about actual living. Guest stars: Brian Patrick Wade, Vernee Watson-Johnson

Season 0 (show/hide)
6	Unraveling the Mystery: A Big Bang Farewell	2019-05-16
Galecki and Cuoco will lead fans on a trip down memory lane, sharing some of the best-kept backstage secrets and personal memories from the past 12 years. They will reveal their favorite moments playing beloved characters Leonard and Penny, and revisit some of the most memorable stories from “The Big Bang Theory Stage.” In addition, the special will feature a tour of the iconic sets, including Leonard and Sheldon’s apartment. This special farewell will include unforgettable clips and interviews to celebrate this beloved series.
5	Comic-Con 2016 Writers Panel	2016-08-18
The Big Bang Theory 2016 Comic Con Writers Panel
4	Comic Con 2015 Writers Panel	2015-07-10
Comic Con 2015 - Big Bang Theory panel
3	It All Started With A Big Bang	2012-04-05
Celebrating the 100th episode of The Big Bang Theory, Rick Edwards looks back at some of the US sitcom's most hilarious and memorable scenes and talks with the cast and crew on the set in Hollywood. The actors share their favourite moments and reveal a few secrets about the making of the show. Guest stars: Rick Edwards (Host)
2	Access All Areas	2012-04-05
Celebrating the 100th episode of US sitcom The Big Bang Theory, Rick Edwards travels to the Hollywood set for an access-all-areas visit, catching up with the cast and learning everything there is to know about the show. This behind-the-scenes special takes fans through everything from the writing of the script to the recording of the show in front of a live audience. Guest stars: Rick Edwards (Host)
1	Unaired Pilot	2007-09-24
The very first pilot of "The Big Bang Theory," starring Amanda Walsh playing Katie, and a female friend called Gilda played by Iris Bahr.

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