When delivery of another collectible leads to Penny’s lashing out at Leonard, he decides it’s time to give up his habit, much to his friends’ protestation.

Leonard and Sheldon each lie to avoid seeing Penny’s concert, but Sheldon’s is a bit too complicated for his own good.

When they’re invited to present at a physics conference, Sheldon’s reluctance to share the credit leads to a tiff between him and Leonard, and Penny’s intervention only exacerbates the situation.

Raj’s parents set him up on a blind date, but just when he discovers he can talk to her, she shows interest in Sheldon.