Sheldon and the gang are confused when a young grad student is attracted to him.

Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.

Leonard asks Penny for advice when his new relationship starts moving too fast.

Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.

Leonard and Penny are drawn together after a disastrous visit from Leonard's mother.

Penny's home business turns into a complete nightmare when Sheldon takes over.

Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.

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.

Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.

When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.

Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.