Penny tags along on Sheldon’s first ever date; Wolowitz finds a new use for a robotic arm.

Leonard tells Penny about how he met Sheldon for the first time…and what happened to the elevator.

Penny gets help from Sheldon in order to understand what Leonard’s work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.

After he’s humiliated on National Public Radio, Sheldon vows to destroy Kripke, while Wolowitz tries not to destroy his new relationship with Bernadette.

A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.

The guys’ plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.

Penny squares off with a new beautiful female neighbor who may become the building’s “new Penny.”

A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.

Penny’s criticism of Wolowitz’s romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for.

Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.

Penny’s first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.

With his friends knowing how sour he acts when sick—and avoiding him as a result—Sheldon is nursed by Penny, who hasn’t a clue what she’s in for.

With Wolowitz AWOL with one of her friends, Penny’s recruited to fill in for him on the guys’ Halo team