The Holiday Summation: After spending Christmas apart, the gang gather at Penny and Leonard's flat and hear about Sheldon and Amy's terrible trip to Texas. (S10 Ep12/24) [AD,S]
The Clean Room Infiltration: Amy hosts a Victorian Christmas Eve dinner, complete with party games. Raj, Leonard and Howard have pigeon problems. (S8 Ep11/24) [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 Ep11/24) [AD,S]
The Santa Simulation: Sheldon unwillingly reveals painful memories of Christmas past when Leonard persuades him to join in with a seasonal game of Dungeons & Dragons. (S6 Ep11/24) [AD,S]
The Maternal Congruence: Leonard is horrified when his mother turns up unannounced for a Christmas visit, and then he finds out that Sheldon knew about her divorce before him. (S3 Ep11/23) [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 Ep11/23) [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 Ep24/24) [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 Ep23/24) [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 Ep24/24) [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 Ep23/24) [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 Ep20/24) [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 Ep19/24) [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 Ep18/24) [AD,S]
The Rothman Disintegration: Sheldon and Kripke argue over who should get Professor Rothman's vacant corner office. Amy buys Penny some art to celebrate their friendship. (S5 Ep17/24) [AD,S]
The Vacation Solution: Sheldon helps Amy in her biology lab after he is forced to use up two weeks of holiday, but he is bored by the tasks that she gives him. (S5 Ep16/24) [AD,S]
The Friendship Contraction: After Sheldon keeps him awake all night, an irate Leonard decides he needs to break the roommate agreement, which formally ends their friendship. (S5 Ep15/24) [AD,S]
The Beta Test Initiation: Leonard and Penny put their relationship through a 'beta test' and report problems with each other as 'bugs'. Sheldon and Amy seek internet fame. (S5 Ep14/24) [AD,S]
The Recombination Hypothesis: In the 100th episode of the US sitcom, Leonard and Penny agree to give their relationship another chance, but they soon start to argue again. (S5 Ep13/24) [AD,S]
The Shiny Trinket Maneuver: When Sheldon is dismissive of Amy's career, Penny, Raj and Leonard teach him that sometimes it's a good idea to pretend to care about things. (S5 Ep12/24) [AD,S]
The Speckerman Recurrence: Leonard confronts the man who bullied him in high school, while Penny realises that she did her fair share of tormenting in the past. (S5 Ep11/24) [AD,S]
The Flaming Spittoon Acquisition: Stuart from the comic book shop invites Amy out on a date. Consumed by jealousy, Sheldon then asks her to be his girlfriend. (S5 Ep10/24) [AD,S]
The Ornithophobia Diffusion: Leonard and Penny attempt to spend time together as friends without anybody else around, while Sheldon faces his fear of birds. (S5 Ep9/24) [AD,S]
The Isolation Permutation: Amy is heartbroken when she finds out that Penny and Bernadette went on a shopping trip to buy bridesmaids' dresses without her. (S5 Ep8/24) [AD,S]
The Good Guy Fluctuation: Leonard doubts his feelings for Priya when he kisses a woman he meets in the comic book shop. The gang pull pranks on Sheldon to celebrate Halloween. (S5 Ep7/24) [AD,S]
The Rhinitis Revelation: Sheldon's mother Mary comes to town and soon becomes a firm favourite with his friends, much to Sheldon's annoyance. (S5 Ep6/24) [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 Ep5/24) [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 Ep4/24) [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 Ep3/24) [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 Ep2/24) [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 Ep1/24) [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 Ep24/24) [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 Ep23/24) [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 Ep22/24) [AD,S]
The Agreement Dissection: Priya uses her legal expertise to dissect the roommate agreement and put Sheldon in his place, and the girls take Sheldon dancing. (S4 Ep21/24) [AD,S]
The Herb Garden Germination: Sheldon and Amy experiment on their friends by spreading gossip, while Howard takes a big step in his relationship with Bernadette. (S4 Ep20/24) [AD,S]
The Zarnecki Incursion: When somebody hacks into Sheldon's online gaming account, he and his friends become determined to locate the culprit. (S4 Ep19/24) [AD,S]
The Prestidigitation Approximation: Leonard must choose between his new girlfriend Priya and his friendship with Penny. Howard drives Sheldon crazy with a magic trick. (S4 Ep18/24) [AD,S]
The Toast Derivation: Sheldon is surprised and disturbed to find out that it's really Leonard who is at the centre of their group of friends and not him. (S4 Ep17/24) [AD,S]
The Cohabitation Formulation: Howard is torn between taking things to the next level with Bernadette and pleasing his mother. Leonard rekindles his relationship with Priya. (S4 Ep16/24) [AD,S]
The Benefactor Factor: A wealthy benefactor at the university makes Leonard consider how far he's willing to go in the name of science. (S4 Ep15/24) [AD,S]
The Thespian Catalyst: Sheldon lectures at the university but worries that the students don't seem to like him. Raj fantasises about his best friend's girlfriend. (S4 Ep14/24) [AD,S]
The Justice League Recombination: The guys slowly warm to Zack and find an enjoyable way to bond with him when they enter a New Year's Eve fancy dress competition together. (S4 Ep11/24) [AD,S]
The Alien Parasite Hypothesis: Amy realises that she has romantic feelings for Zack. Raj and Howard compete to prove who would make the better superhero. (S4 Ep10/24) [AD,S]
The Boyfriend Complexity: When Penny's father visits, Leonard discovers that her parents still think that he and Penny are a couple, so he takes advantage of the situation. (S4 Ep9/24) [AD,S]
The 21-Second Excitation: The gang's plans to attend a film screening are scuppered by Sheldon's nemesis Wil Wheaton. Penny and Bernadette invite Amy to her first slumber party. (S4 Ep8/24) [AD,S]
The Apology Insufficiency: Leonard thinks his dating problems are due to a lack of confidence, and vows to be self-assured around attractive women. Howard is called by the FBI. (S4 Ep7/24) [AD,S]
The Irish Pub Formulation: A visit from Raj's sister Priya creates tension among the guys, especially when Leonard asks Sheldon to conceal his romantic past with her. (S4 Ep6/24) [AD,S]
The Desperation Emanation: Leonard realises he's the only one of the gang with no girlfriend. Sheldon wants to get rid of his when she hatches a plan for him to meet her mother. (S4 Ep5/24) [AD,S]