The Big Bang Theory, The Good Guy Fluctuation

On the fifth season premiere, Penny worries that she's screwed things up permanently with her friends after her night with Raj, while Sheldon takes command of the paintball team.

A battle of wills between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya (Aarti Mann).

Attending a co-worker's wedding, Leonard and Amy (Mayim Bialik) get to know each other better, while Howard and Bernadette spend the weekend with Mrs Wolowitz!

When Raj is upset he's the only one of the four guys who's not in a relationship, Penny sets out to find the perfect date, introducing him to Emily, a girl he can actually talk to!

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

Sheldon craves attention from his visiting mother.

Sheldon tries to spook his friends on Halloween.

Bernadette and Penny shop for wedding dresses without Amy.

Sheldon must overcome his fear of birds.

Sheldon becomes jealous when Stuart asks Amy for a date.

Leonard comes face-to-face with his high school bully.

Sheldon gets in trouble with Amy, and it's up to Penny to teach him how to be a better boyfriend. Howard, meanwhile, must come to grips with Bernadette's dislike of children.

Everything might change when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two on the 100th episode of the series.

Leonard and Penny 'beta test' their relationship.

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Howard tries to pick his astronaut nickname. NASA astronaut Mike Massimino guest stars.

When Sheldon is forced to take a vacation by the university, he goes to work with Amy in her neurobiology lab.

When a corner office at the University opens up, Sheldon must compete for it with his office nemesis, Barry Kripke. Meanwhile, Penny receives an unusual gift from Amy.

A change in Sheldon's routine forces him to re-evaluate his entire life, when his barber is sick. Meanwhile, Howard rethinks his decision to go into space after astronaut training.

Sheldon chooses to participate in a guys-only weekend Star Wars gaming marathon rather than go with Amy to her aunt's birthday party -- and gets a lesson from Penny and Amy.

It's a dream come true for Sheldon when he has a close encounter with his hero, Mr Spock -- legendary sci-fi icon Leonard Nimoy.

Sheldon has a chance to meet his hero, Stephen Hawking.

Howard's wedding plans are in jeopardy after the guys (and Wil Wheaton) throw him a bachelor party and details of his sexual history are leaked online.

When NASA reschedules Howard's mission and puts his wedding plans in jeopardy, he's forced to face his fears and Bernadette's dad (Casey Sander).

When Howard and Bernadette decide they want to be married before his NASA space launch, the gang rushes to put on a wedding, on the fifth season finale.