The Big Bang Theory
About the Show
Arch-nerds Leonard and Sheldon may know more than their fair share about subatomic particles, but when it comes to people in general, and women in particular, they're absolutely clueless...
Series 4 Summary
In this series Sheldon goes on his first ever date, Wolowitz finds a new use for a robotic arm, the gang meet Apple co-founder Steve Wozniak and Sheldon calculates how many relationships Penny has had.
Episode 1 - The Robotic Manipulation
Penny tags along on Sheldon's first ever date, with a woman he's been texting for months. Meanwhile, Howard finds a new use for a robotic arm.
Episode 2 - The Cruciferous Vegetable Amplification
Sheldon realises he won't live long enough to download his consciousness into a robot body, so he tries to extend his lifespan
Episode 3 - The Zazzy Substitution
The guys are concerned when a heartbroken Sheldon starts bulk-buying cats after he breaks up with Amy. Leonard realises he must get Sheldon's mother to visit.
Episode 4 - The Hot Troll Deviation
An embarrassing secret of Howard's comes to light as he tries to win back Bernadette. Meanwhile, Sheldon and Raj engage in a battle of wills.
Episode 5 - The Desperation Emanation
Leonard realises that he's the only one of the gang without a girlfriend, while Sheldon wants to get rid of his when she hatches a plan for him to meet her mother.
Episode 6 - The Irish Pub Formulation
A visit from Raj's sister Priya creates tension among the guys - especially when Leonard coaxes Sheldon into hiding his romantic past with Priya from the rest of the gang.
Episode 7 - The Apology Insufficiency
Leonard believes his problem with women stems from a lack of confidence, and vows to be more self-assured around attractive women. Meanwhile, Howard has a call from the FBI.
Episode 8 - The 21-Second Excitation
Sheldon's movie-going plans are scuppered by his nemesis Wil Wheaton. Penny and Bernadette invite Amy to her first slumber party.
Episode 9 - The Boyfriend Complexity
When Penny's father comes to visit, Leonard discovers that her parents still think that he and Penny are a couple
Episode 10 - The Alien Parasite Hypothesis
Amy discovers that she has feelings for Penny's ex-boyfriend Zack. Meanwhile, Raj and Howard try to prove who would be the better superhero.
Episode 11 - The Justice League Recombination
The guys warm to Penny's new boyfriend Zack and find a way to bond with him.
Episode 12 - The Bus Pants Utilization
Leonard's idea for a smartphone application derails his friendship with Sheldon as they fight for control of the project
Episode 13 - The Love Car Displacement
Howard feels threatened when Bernadette runs into her hulk of an ex-boyfriend at a science conference
Episode 14 - 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.
Episode 15 - The Benefactor Factor
A wealthy benefactor at the university makes Leonard ponder just how far he's willing to go in the name of science.
Episode 16 - The Cohabitation Formulation
Howard is torn between taking things to the next level with Bernadette, and pleasing his mother. Leonard rekindles his relationship with Raj's sister, Priya.
Episode 17 - The Toast Derivation
Sheldon gets a new group of friends when the gang start hanging out at Raj's more often and he realises that it's actually Leonard who is the centre of their social group and not him.
Episode 18 - The Prestidigitation Approximation
Leonard must choose between his new girlfriend Priya, and his friendship with Penny. Meanwhile, Howard drives Sheldon crazy with a magic trick.
Episode 19 - The Zarnecki Incursion
When someone hacks Sheldon's online gaming account, the guys go on a quest to find the culprit.
Episode 20 - 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.
Episode 21 - The Agreement Dissection
Priya uses her legal nous to dissect the roommate agreement and put Sheldon in his place. Meanwhile, the girls take Sheldon dancing.
Episode 22 - The Wildebeest Implementation
Raj attempts to cure his social anxiety disorder around talking to women, while Penny uses Bernadette to spy on Leonard and his girlfriend.
Episode 23 - The Engagement Reaction
Howard finally tells him mum that he's engaged to Bernadette. Unfortunately, the news lands his mum in hospital.
Episode 24 - The Roomate Transmogrification
In the series four finale, Raj moves in with Sheldon after overhearing Leonard and Priya's Star Trek bedroom fantasy