The Cooper Extraction: Sheldon has to go back to Texas when his sister goes into labour. While he's away, the gang gather at the flat to decorate the Christmas tree. (S7 Ep11) [AD,S]
The Cooper Extraction: Sheldon has to go back to Texas when his sister goes into labour. While he's away, the gang gather at the flat to decorate the Christmas tree. (S7 Ep11) [AD,S]
The Codpiece Topology: Seeing Penny out on a date with another guy sends a distressed Leonard rushing back to Leslie Winkle, much to Sheldon's dismay. (S2 Ep2) [AD,S]
The Barbarian Sublimation: Penny becomes addicted to an online game based on the world of Conan the Barbarian and begins to pester Sheldon for advice. (S2 Ep3) [AD,S]
The Cognition Regeneration: Leonard isn't happy when he finds out that Penny is considering accepting a job offer from her ex-boyfriend Zack. (S10 Ep22/24) [AD,S]
The Separation Agitation: Howard and Bernadette are upset when they leave Halley at the nursery. Bert the geologist introduces his girlfriend to the gang. (S10 Ep21/24) [AD,S]
The Cognition Regeneration: Leonard isn't happy when he finds out that Penny is considering accepting a job offer from her ex-boyfriend Zack. (S10 Ep22/24) [AD,S]
The Wildebeest Implementation: Raj attempts to overcome his anxiety about talking to women, while Penny uses Bernadette to spy on Leonard and his girlfriend. (S4 Ep22) [AD,S]
The Engagement Reaction: Howard finally tells his mother that he's engaged to Bernadette. Unfortunately, the news lands his mum in hospital. (S4 Ep23) [AD,S]
The Roommate Transmogrification: Raj decides to move in with Sheldon after hearing Leonard and Priya engaging in a Star Trek bedroom fantasy. (S4 Ep24) [AD,S]
The Wildebeest Implementation: Raj attempts to overcome his anxiety about talking to women, while Penny uses Bernadette to spy on Leonard and his girlfriend. (S4 Ep22) [AD,S]
The Skank Reflex Analysis: Penny worries that she's screwed things up with her friends after her night with Raj. Sheldon takes command of the paintball team. (S5 Ep1) [AD,S]
The Engagement Reaction: Howard finally tells his mother that he's engaged to Bernadette. Unfortunately, the news lands his mum in hospital. (S4 Ep23) [AD,S]
The Roommate Transmogrification: Raj decides to move in with Sheldon after hearing Leonard and Priya engaging in a Star Trek bedroom fantasy. (S4 Ep24) [AD,S]
The Skank Reflex Analysis: Penny worries that she's screwed things up with her friends after her night with Raj. Sheldon takes command of the paintball team. (S5 Ep1) [AD,S]
The Werewolf Transformation: Sheldon's well-organised world is turned upside down when he learns that the barber who has cut his hair for years is ill in hospital. (S5 Ep18) [AD,S]
The Weekend Vortex: Amy is upset when Sheldon breaks his promise to attend her aunt's birthday party in order to join the guys for a Star Wars video game marathon instead. (S5 Ep19) [AD,S]
The Transporter Malfunction: Penny buys Leonard and Sheldon some Star Trek memorabilia, but she is irked when they refuse to remove the toys from their packaging. (S5 Ep20) [AD,S]
The Hawking Excitation: When Stephen Hawking comes to lecture at the university, Howard is given the task of maintaining his wheelchair, which makes Sheldon envious. (S5 Ep21) [AD,S]
The Work Song Nanocluster: Penny's home-based business selling hair accessories gets out of hand when an overexcited Sheldon takes charge of production. (S2 Ep18) [AD,S]
The Dead Hooker Juxtaposition: Penny develops a rivalry with a sexy female neighbour who moves into the apartment building and threatens to become the 'new Penny'. (S2 Ep19) [AD,S]
The Hofstadter Isotope: Leonard is devastated when Stuart from the comic book shop chats up Penny. Even worse, she doesn't mind. Sheldon tries to scupper the budding romance. (S2 Ep20) [AD,S]
The Vegas Renormalization: Leonard and Raj take a heartbroken Howard to Las Vegas, leaving Sheldon locked out of his flat and forced to stay with Penny. (S2 Ep21) [AD,S]
The Occupation Recalibration: Penny quits her job at the restaurant to pursue her acting career full-time. Bernadette accidentally destroys one of Howard's comics. (S7 Ep13) [AD,S]
The Convention Conundrum: After the guys miss out on Comic-Con tickets, Sheldon decides to hold his own comic book convention. The girls take tea at a swanky hotel. (S7 Ep14) [AD,S]
The Occupation Recalibration: Penny quits her job at the restaurant to pursue her acting career full-time. Bernadette accidentally destroys one of Howard's comics. (S7 Ep13) [AD,S]
The Convention Conundrum: After the guys miss out on Comic-Con tickets, Sheldon decides to hold his own comic book convention. The girls take tea at a swanky hotel. (S7 Ep14) [AD,S]
The Cooper-Hofstadter Polarization: Sheldon and Leonard fall out when they're asked to collaborate at a physics conference. Penny tries to help but just makes things worse. (S1 Ep9) [AD,S]
The Cooper-Hofstadter Polarization: Sheldon and Leonard fall out when they're asked to collaborate at a physics conference. Penny tries to help but just makes things worse. (S1 Ep9) [AD,S]
The Occupation Recalibration: Penny quits her job at the restaurant to pursue her acting career full-time. Bernadette accidentally destroys one of Howard's comics. (S7 Ep13) [AD,S]
The Occupation Recalibration: Penny quits her job at the restaurant to pursue her acting career full-time. Bernadette accidentally destroys one of Howard's comics. (S7 Ep13) [AD,S]
The Griffin Equivalency: Full of confidence after being named one of People magazine's '30 to Watch Under 30', Raj hits on Penny and becomes impossibly arrogant. (S2 Ep4) [AD,S]
The Euclid Alternative: When Leonard can't drive Sheldon to and from work, the friends stage an intervention to overcome Sheldon's fear of getting behind the wheel. (S2 Ep5) [AD,S]
The Gyroscopic Collapse: Amy is offered a fellowship at Princeton, Raj makes new living arrangements, and the guys' gyroscope project spins out of control. (S10 Ep23/24) [AD,S]
The Long Distance Dissonance: The gang worry when Sheldon's former admirer, Dr Ramona Nowitzki, turns up while Amy is away working at Princeton. (S10 Ep24/24) [AD,S]
The Gyroscopic Collapse: Amy is offered a fellowship at Princeton, Raj makes new living arrangements, and the guys' gyroscope project spins out of control. (S10 Ep23/24) [AD,S]
The Long Distance Dissonance: The gang worry when Sheldon's former admirer, Dr Ramona Nowitzki, turns up while Amy is away working at Princeton. (S10 Ep24/24) [AD,S]
The Infestation Hypothesis: Amy is stuck in the middle of a battle of wills between Penny and Sheldon. Leonard and Priya try to spice up their long-distance relationship. (S5 Ep2) [AD,S]
The Pulled Groin Extrapolation: Leonard goes to a colleague's wedding as Amy's date. Howard tries to convince Bernadette to live with his mum after they get married. (S5 Ep3) [AD,S]
The Wiggly Finger Catalyst: Raj begins to get upset that he's the only one of the four guys not in a relationship, so Penny sets out to find him the perfect date. (S5 Ep4) [AD,S]
The Infestation Hypothesis: Amy is stuck in the middle of a battle of wills between Penny and Sheldon. Leonard and Priya try to spice up their long-distance relationship. (S5 Ep2) [AD,S]
The Russian Rocket Reaction: Sheldon's old nemesis Wil Wheaton returns and invites everyone to a housewarming party. But Sheldon threatens to 'de-friend' Leonard if he attends. (S5 Ep5) [AD,S]
The Pulled Groin Extrapolation: Leonard goes to a colleague's wedding as Amy's date. Howard tries to convince Bernadette to live with his mum after they get married. (S5 Ep3) [AD,S]
The Wiggly Finger Catalyst: Raj begins to get upset that he's the only one of the four guys not in a relationship, so Penny sets out to find him the perfect date. (S5 Ep4) [AD,S]
The Russian Rocket Reaction: Sheldon's old nemesis Wil Wheaton returns and invites everyone to a housewarming party. But Sheldon threatens to 'de-friend' Leonard if he attends. (S5 Ep5) [AD,S]
The Stag Convergence: Leonard, Sheldon and Raj throw a bachelor party for Howard, during which some stories about his sexual history are accidentally revealed. (S5 Ep22) [AD,S]
The Launch Acceleration: When NASA inform Howard that his space mission has been rescheduled to an earlier date, he tries to use the wedding as an excuse not to go. (S5 Ep23) [AD,S]
The Countdown Reflection: Bernadette decides that she wants to get married to Howard before his NASA space mission, but can they get organised in time? (S5 Ep24) [AD,S]
The Stag Convergence: Leonard, Sheldon and Raj throw a bachelor party for Howard, during which some stories about his sexual history are accidentally revealed. (S5 Ep22) [AD,S]
The Date Night Variable: Howard gets caught in a row between his mum and Bernadette while he's at the International Space Station. Sheldon invites Raj along on a date with Amy. (S6 Ep1) [AD,S]
The Launch Acceleration: When NASA inform Howard that his space mission has been rescheduled to an earlier date, he tries to use the wedding as an excuse not to go. (S5 Ep23) [AD,S]
The Countdown Reflection: Bernadette decides that she wants to get married to Howard before his NASA space mission, but can they get organised in time? (S5 Ep24) [AD,S]
The Date Night Variable: Howard gets caught in a row between his mum and Bernadette while he's at the International Space Station. Sheldon invites Raj along on a date with Amy. (S6 Ep1) [AD,S]
The Classified Materials Turbulence: Things look up for Leonard when Penny makes a surprising revelation on her second date with Stuart. Howard sees a flaw in his NASA project. (S2 Ep22) [AD,S]
The Monopolar Expedition: Leonard and Penny reconsider their feelings for each other, but then Leonard is offered the opportunity to spend the summer working at the North Pole. (S2 Ep23) [AD,S]
The Electric Can Opener Fluctuation: Leonard's attempts to woo Penny are constantly thwarted. Sheldon heads to Texas after learning his friends meddled with his expedition data. (S3 Ep1) [AD,S]
The Jiminy Conjecture: Leonard and Penny feel awkward around each other after their romantic liaison, while Sheldon and Howard take bets to determine a species of cricket. (S3 Ep2) [AD,S]
The Locomotive Manipulation: Love is in the air when Amy convinces Sheldon to join her for a romantic train trip to Napa Valley to celebrate Valentine's Day. (S7 Ep15) [AD,S]
The Table Polarization: Leonard buys a dining table for the flat but Sheldon objects to such a big change inside his home. Meanwhile, Howard gets the chance to return to space. (S7 Ep16) [AD,S]
The Locomotive Manipulation: Love is in the air when Amy convinces Sheldon to join her for a romantic train trip to Napa Valley to celebrate Valentine's Day. (S7 Ep15) [AD,S]
The Table Polarization: Leonard buys a dining table for the flat but Sheldon objects to such a big change inside his home. Meanwhile, Howard gets the chance to return to space. (S7 Ep16) [AD,S]
The Locomotive Manipulation: Love is in the air when Amy convinces Sheldon to join her for a romantic train trip to Napa Valley to celebrate Valentine's Day. (S7 Ep15) [AD,S]
The Locomotive Manipulation: Love is in the air when Amy convinces Sheldon to join her for a romantic train trip to Napa Valley to celebrate Valentine's Day. (S7 Ep15) [AD,S]
The Proposal Proposal: Amy must decide whether or not to marry Sheldon and gives him an answer to his proposal. Howard and Bernadette struggle with some unexpected news. (S11 Ep1) [AD,S]
The Retraction Reaction: Leonard angers the university during an embarrassing interview. Amy and Bernadette must hide their success from Sheldon and Howard. (S11 Ep2) [AD,S]
The Relaxation Integration: Amy tries to convince Sheldon that he has a more laid-back side. Raj and Stuart compete to woo Bernadette's new colleague Ruchi. (S11 Ep3) [AD,S]
The Proposal Proposal: Amy must decide whether or not to marry Sheldon and gives him an answer to his proposal. Howard and Bernadette struggle with some unexpected news. (S11 Ep1) [AD,S]
The Explosion Implosion: Howard and Sheldon bond on a trip to the desert to launch a model rocket. Leonard is annoyed when his mother befriends Penny. (S11 Ep4) [AD,S]
The Retraction Reaction: Leonard angers the university during an embarrassing interview. Amy and Bernadette must hide their success from Sheldon and Howard. (S11 Ep2) [AD,S]
The Relaxation Integration: Amy tries to convince Sheldon that he has a more laid-back side. Raj and Stuart compete to woo Bernadette's new colleague Ruchi. (S11 Ep3) [AD,S]
The Explosion Implosion: Howard and Sheldon bond on a trip to the desert to launch a model rocket. Leonard is annoyed when his mother befriends Penny. (S11 Ep4) [AD,S]
The Cooper-Nowitzki Theorem: Sheldon's friends are mystified when a younger student is attracted to him, and her intense devotion soon becomes too much to bear. (S2 Ep6) [AD,S]
The Panty PiÄnata Polarization: Sheldon bans Penny from the flat for numerous minor infractions, so she retaliates. Howard and Raj search for the America's Next Top Model house. (S2 Ep7) [AD,S]
The White Asparagus Triangulation: Sheldon is delighted that Leonard has finally found a girlfriend who matches up to his high standards... Perhaps a little too delighted. (S2 Ep9) [AD,S]
The Vartabedian Conundrum: Leonard goes to Penny for help when his relationship with Stephanie takes off faster than he'd like, but will he act on her advice? (S2 Ep10) [AD,S]
The Bath Item Gift Hypothesis: At Christmas, Leonard's hunky colleague starts dating Penny, while Sheldon's obsession with gift-giving etiquette torments everyone. (S2 Ep11) [AD,S]
The Killer Robot Instability: Kripke challenges the boys to a robot duel, while Howard is devastated when Penny finally tells him what she thinks of his chauvinism. (S2 Ep12) [AD,S]
The Friendship Algorithm: Sheldon develops a scientific procedure for making friends when he discovers that Kripke has control of a new supercomputer at the university. (S2 Ep13) [AD,S]
The Financial Permeability: When Sheldon lends Penny some money, it brings her ex-boyfriend Kurt back into her life, with negative consequences for the gang. (S2 Ep14) [AD,S]
The Euclid Alternative: When Leonard can't drive Sheldon to and from work, the friends stage an intervention to overcome Sheldon's fear of getting behind the wheel. (S2 Ep5) [AD,S]
The Griffin Equivalency: Full of confidence after being named one of People magazine's '30 to Watch Under 30', Raj hits on Penny and becomes impossibly arrogant. (S2 Ep4) [AD,S]
The Barbarian Sublimation: Penny becomes addicted to an online game based on the world of Conan the Barbarian and begins to pester Sheldon for advice. (S2 Ep3) [AD,S]
The Codpiece Topology: Seeing Penny out on a date with another guy sends a distressed Leonard rushing back to Leslie Winkle, much to Sheldon's dismay. (S2 Ep2) [AD,S]
Pilot: The first ever episode of the hit sitcom. Leonard and Sheldon's geeky world is shaken up by the arrival of a beautiful new neighbour. (S1 Ep1) [AD,S]
The Bad Fish Paradigm: Penny opens up to a reluctant Sheldon after a less-than-stellar first date with Leonard, putting him in the awkward position of having to keep a secret. (S2 Ep1) [AD,S]
The Tangerine Factor: When Penny breaks up with her boyfriend, Leonard plucks up the courage to ask her out. And each of them turns to Sheldon for advice about their date. (S1 Ep17) [AD,S]
The Peanut Reaction: Penny throws a surprise party for Leonard, with help from Howard and Raj, but Sheldon's indulgence in an electronics shop throws her off track. (S1 Ep16) [AD,S]
The Shiksa Indeterminacy: Leonard, Raj and Howard all fall heavily for Sheldon's twin sister, but when Leonard comes up with a plan to win her heart, it's derailed by Sheldon. (S1 Ep15) [AD,S]
The Stockholm Syndrome: Howard and Bernadette go on a trip without their children, Leonard and Penny try to keep a secret, and Raj makes a new friend. (S12 Ep24) [AD,S]
The Change Constant: Sheldon and Amy stay up late awaiting a phone call that could bring big news from the Nobel Committee: are their lives about to change? (S12 Ep23) [AD,S]
The Nerdvana Annihilation: When Penny makes fun of Leonard's habit of collecting goofy memorabilia, his friends kick up a fuss and try to keep him on the side of the nerds. (S1 Ep14) [AD,S]
The Bat Jar Conjecture: Sheldon is ousted from the gang's Physics Bowl quiz team, so he decides to prove his superiority by forming his own team for the event. (S1 Ep13) [AD,S]
The Pancake Batter Anomaly: Penny volunteers to nurse Sheldon when he's sick. But his friends, who know how miserable he is when he's ill, stay well away. (S1 Ep11) [AD,S]
The Maternal Conclusion: Leonard is surprised when his mother Beverly comes to visit and is kind to him, until he finds out the real reason she's there. (S12 Ep22) [AD,S]
The Plagiarism Schism: Barry Kripke finds proof that Dr Pemberton plagiarised his thesis in college. Should Sheldon and Amy turn in their rival? (S12 Ep21) [AD,S]
The Loobenfeld Decay: Leonard and Sheldon each tell a lie to avoid going to see Penny singing on stage in a production of Rent, but Sheldon's fib gets out of control. (S1 Ep10) [AD,S]
The Cooper-Hofstadter Polarization: Sheldon and Leonard fall out when they're asked to collaborate at a physics conference. Penny tries to help but just makes things worse. (S1 Ep9) [AD,S]
The Grasshopper Experiment: Raj panics when his parents arrange a blind date for him. But he discovers that he can talk to her - after a few drinks. (S1 Ep8) [AD,S]
The Dumpling Paradox: When Howard seduces Penny's friend and spends the night with her in Penny's flat, Penny asks if she can sleep on Leonard and Sheldon's sofa. (S1 Ep7) [AD,S]
The Decision Reverberation: Raj publishes a paper that suggests he may have discovered alien life. Penny encourages Leonard to stand up for himself. (S12 Ep20) [AD,S]
The Inspiration Deprivation: Amy has a meltdown when she feels the pressure of what it would mean for women everywhere if she were to win a Nobel Prize. (S12 Ep19) [AD,S]
The Middle Earth Paradigm: Penny's Halloween party puts Leonard, Sheldon, Howard and Raj through a demanding new test of their social skills. (S1 Ep6) [AD,S]
The Hamburger Postulate: Leonard thinks he's been wasting his time on Penny, so he turns his attention to Leslie. Sheldon's uncomfortable with a change to his hamburger routine. (S1 Ep5) [AD,S]
The Luminous Fish Effect: Getting fired forces Sheldon to ponder life outside physics, so Leonard has to take drastic action to snap his friend out of his reverie. (S1 Ep4) [AD,S]
The Fuzzyboots Corollary: Leonard is upset when he discovers that Penny is seeing someone, so he plucks up the courage to ask a woman out on a date. (S1 Ep3) [AD,S]
The Laureate Accumulation: When their academic competitors charm America on a publicity tour, Sheldon and Amy try to get some Nobel laureates on their side. (S12 Ep18) [AD,S]
The Conference Valuation: Penny and Bernadette go to San Diego for a sales convention, leaving Howard in charge of Michael and Halley while they're away. (S12 Ep17) [AD,S]
The D & D Vortex: When the gang find out that Wil Wheaton is hosting a celebrity game of Dungeons & Dragons at his home, deception and betrayal take hold. (S12 Ep16) [AD,S]
The Donation Oscillation: Penny attempts to sabotage Leonard's efforts to help her ex-boyfriend Zack and his wife Marissa have a family of their own. (S12 Ep15) [AD,S]
The Meteorite Manifestation: Sheldon is thrilled to help Howard and Bernadette with some bureaucratic paperwork, until he realises that they're breaking the law. (S12 Ep14) [AD,S]
The Confirmation Polarization: Sheldon and Amy are thrilled when their super-asymmetry theory is proved correct. Bernadette enjoys some big success at work. (S12 Ep13) [AD,S]
The Propagation Proposition: Penny's ex-boyfriend Zack and his wife want a baby, but when they encounter fertility problems, they ask Leonard for his help. (S12 Ep12) [AD,S]
The Paintball Scattering: Jealousy, trust issues and tension among the couples in the gang cause mayhem when Penny and Leonard organise a paintball game. (S12 Ep11) [AD,S]
The VCR Illumination: Sheldon and Amy are still upset about their theory being disproven, but a video tape from Sheldon's past inspires him not to give up. (S12 Ep10) [AD,S]
The Citation Negation: Sheldon and Amy get some devastating news. Bernadette asks Stuart's girlfriend Denise to teach her how to beat Howard at a video game. (S12 Ep9) [AD,S]
The Consummation Deviation: Sheldon aims to bond with Amy's father, but Howard lures Mr Fowler away with his magic tricks. Raj and Anu try to get physical. (S12 Ep8) [AD,S]
The Grant Allocation Derivation: Leonard is made responsible for distributing extra grant money. Bernadette turns the garden playhouse into a hideaway to escape her family. (S12 Ep7) [AD,S]
The Romance Recalibration: Penny thinks that Leonard has stopped making an effort in their relationship, so she decides to go away for a spa weekend with Amy. (S10 Ep13) [AD,S]
The Bitcoin Entanglement: Sheldon seeks revenge when the guys cut him out of a potentially valuable investment. A secret about Leonard and Penny is revealed. (S11 Ep9) [AD,S]
The Tesla Recoil: Leonard and Howard learn that Sheldon went to work with the military behind their backs. Bernadette thinks Ruchi's trying to steal her job. (S11 Ep8) [AD,S]
The Geology Methodology: Sheldon and Bert collaborate on a research project, but Sheldon feels embarrassed to be associated with the study of geology. (S11 Ep7) [AD,S]
The Retraction Reaction: Leonard angers the university during an embarrassing interview. Amy and Bernadette must hide their success from Sheldon and Howard. (S11 Ep2) [AD,S]
The Proposal Proposal: Amy must decide whether or not to marry Sheldon and gives him an answer to his proposal. Howard and Bernadette struggle with some unexpected news. (S11 Ep1) [AD,S]
The Recollection Dissipation: Sheldon collaborates on two projects - one with Leonard and Howard, plus another with Amy - pushing himself to the limit. (S10 Ep20) [AD,S]
The Collaboration Fluctuation: Leonard, Penny and Raj settle into their new living arrangement, and Sheldon expresses an interest in Amy's professional life. (S10 Ep19) [AD,S]
The Escape Hatch Identification: Leonard and Penny offer Sheldon's old room to Raj when he's forced to move out of his flat, leading to unexpected conflict. (S10 Ep18) [AD,S]