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.

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

An embarrassing secret of Wolowitz’s comes to light, while Sheldon and Raj have a small war at work.

Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.

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

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.

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

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

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

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.

Meredith is sent into a state of panic when Derek finds her mother’s diary in the house. Meanwhile, Callie stresses while preparing for her first date with Erica. Later, Cristina…

Jackie meets the local star while at the salon with Fez: talk show host Christine St. George. Her new goal in life is to be Christine’s co-anchor on “What’s Up…

Red lets Hyde in on a Valentine’s Day secret; Christine opens up to Jackie about her love life; and Randy has big plans for a date.