E2 • The Infestation Hypothesis

E1 • The Skank Reflex Analysis

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.

21m • 2011

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.

E2 • The Infestation Hypothesis

A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.

19m • 2011

A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.

E3 • The Pulled Groin Extrapolation

Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.

19m • 2011

Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.

E4 • The Wiggly Finger Catalyst

Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.

19m • 2011

Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.

E5 • The Russian Rocket Reaction

Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity.

21m • 2011

Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity.

E6 • The Rhinitis Revelation

Sheldon's mother, Mary Cooper, comes to visit, but Sheldon is annoyed that she spends time with the rest of the gang instead of catering to his every demand.

20m • 2011

Sheldon's mother, Mary Cooper, comes to visit, but Sheldon is annoyed that she spends time with the rest of the gang instead of catering to his every demand.

E7 • The Good Guy Fluctuation

A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween.

19m • 2011

A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween.

E8 • The Isolation Permutation

Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her.

20m • 2011

Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her.

E9 • The Ornithophobia Diffusion

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.

20m • 2011

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.

E10 • The Flaming Spittoon Acquisition

Sheldon becomes jealous when Stuart asks Amy for a date.

20m • 2011

Sheldon becomes jealous when Stuart asks Amy for a date.

E11 • The Speckerman Recurrence

Leonard must face his fears after being contacted by his high school tormentor.

19m • 2011

Leonard must face his fears after being contacted by his high school tormentor.

E12 • The Shiny Trinket Maneuver

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.

20m • 2011

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.

E13 • The Recombination Hypothesis

Leonard, having broken up with Priya, asks Penny out to a spur-of the-moment romantic dinner for two.

20m • 2011

Leonard, having broken up with Priya, asks Penny out to a spur-of the-moment romantic dinner for two.

E14 • The Beta Test Initiation

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.

20m • 2011

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.

E15 • The Friendship Contraction

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname.

20m • 2011

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname.

E16 • The Vacation Solution

When Sheldon is forced to take his vacation, he goes to work with Amy in her neurobiology lab.

20m • 2011

When Sheldon is forced to take his vacation, he goes to work with Amy in her neurobiology lab.

E17 • The Rothman Disintegration

Penny is horrified when Amy gives her a gift: a huge, quite horrible painting of the two of them. With no good way to avoid displaying it, she only hangs it up when Amy is over.

20m • 2011

Penny is horrified when Amy gives her a gift: a huge, quite horrible painting of the two of them. With no good way to avoid displaying it, she only hangs it up when Amy is over.

E18 • The Werewolf Transformation

Sheldon becomes agitated when his regular barber is out sick. Astronaut training causes Howard to reconsider wanting to go into space.

20m • 2011

Sheldon becomes agitated when his regular barber is out sick. Astronaut training causes Howard to reconsider wanting to go into space.

E19 • The Weekend Vortex

Sheldon must choose between joining Amy at her aunt's birthday party or playing videogames all weekend with the guys.

19m • 2011

Sheldon must choose between joining Amy at her aunt's birthday party or playing videogames all weekend with the guys.

E20 • The Transporter Malfunction

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.

20m • 2011

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.

E21 • The Hawking Excitation

When Wolowitz gets to work with Stephen Hawking, Sheldon is willing to do anything to meet his hero.

18m • 2011

When Wolowitz gets to work with Stephen Hawking, Sheldon is willing to do anything to meet his hero.

E22 • The Stag Convergence

After the guys throw Howard a bachelor party, Bernadette reconsiders marrying him after learning about his sexual history.

21m • 2011

After the guys throw Howard a bachelor party, Bernadette reconsiders marrying him after learning about his sexual history.

E23 • The Launch Acceleration

When NASA moves up Howard's mission, he must face his fears and Bernadette's dad, thus putting the wedding plans in jeopardy.

20m • 2011

When NASA moves up Howard's mission, he must face his fears and Bernadette's dad, thus putting the wedding plans in jeopardy.

E24 • The Countdown Reflection

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.

20m • 2011

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.