The Big Bang Theory

Leonard and Amy take an unexpected road trip to Arizona to pick up Sheldon. Meanwhile, Penny interviews for a job at Bernadette's company.

When Sheldon is forced to teach a class, Howard surprises everyone by taking it. Meanwhile, Amy sees an opportunity to play both sides.

Leonard and Penny try to prove Sheldon wrong after he says that he and Amy are a superior couple.

Penny tries to figure out why Emily doesn’t like her; the guys consider becoming part-owners in Stuart's comic book store.

With the girls away in Vegas for the weekend, the guys try to invent “the next big thing,” but only come up with new ways to procrastinate.

Sheldon and Raj see if they can survive intense heat, and each other, when they venture deep underground in the name of science.

The guys try to help Penny out of an awkward work dilemma, after her flirtatious sales techniques work a little too well on a doctor.

When the gang recreates prom night on the roof of their building, Sheldon feels pressure to participate in all the romantic traditions.

Sheldon is in need of sympathy when Leonard gets minor surgery; Raj’s parents’ divorce leads Howard & Bernadette to work on their marriage.

As Sheldon records the final installment of “Fun with Flags,” Bernadette is shocked to learn of her co-workers’ true feelings from Penny.

Leonard and Wolowitz nearly come to blows and turn to Raj for help in dealing with a work emergency.

When the guys finally agree to do something the girls like, it leads to a confrontation between Leonard and Sheldon.

Sheldon worries his comfortable lifestyle is preventing him from achieving scientific progress so he asks his friends to make him miserable.

After Leonard and Sheldon co-publish a physics paper, they must defend themselves against criticism from an online bully.

Wolowitz receives some shocking news as everyone prepares for the reopening of Stuart’s comic book store.

When the gang hears about an experiment designed to make participants fall in love, Sheldon and Penny put it to the test.

Amy learns that Sheldon has applied for a one-way mission to colonize Mars. Leonard surprises Penny with a very ‘adult’ purchase.

Friction ensues when a magazine fails to mention Leonard in an article about the paper he co-wrote with Sheldon.

When Leonard and Sheldon are invited to speak at UC Berkeley, they try to sneak on to George Lucas’s Skywalker Ranch to meet their idol.

Wolowitz is shocked when a man claiming to be his half-brother shows up at his door. Sheldon & Amy reach a crossroads in their relationship.

When Raj is asked to create a message in case a NASA mission discovers alien life, the guys fight over what he should do.

Howard questions his engineering abilities, while Raj pits his parents against each other when his father cuts him off financially.

Both Sheldon and Leonard's mothers visit to see their sons get an award; Bernadette wants help around their new home from Howard and Stuart.

In the season finale, Sheldon presses Leonard and Penny to choose a date for their wedding, while dealing with his own changes with Amy.