Leonard gets forced to chose between his new girlfriend Priya or Penny. He then drives Sheldon crazy with his magic trick.

Sheldon gets upset after he realizes that Leonard is the center of their group of friends.

Wolowitz starts considering taking his relationship with Bernadette to the next level. Meanwhile, Leonard and Raj’s sister rekindle their relationship.

Leonard starts questioning himself about what is he willing to do for science after meeting a very wealthy donor.

Penny gives Sheldon some acting lessons since he is trying to become a better teacher. Meanwhile, Koothrappali starts fantasizing about his friend’s girlfriend.

Bernadette runs into her ex boyfriend (Rick Fox) while attending a science event with Wolowitz.

Leonard gets an idea about a new smartphone application which derails his friendship with Sheldon.

The guys enter a costume contest with Penny’s new boyfriend.

Amy realizes she has feelings for Penny’s ex; Koothrappali and Wolowitz try to prove who would be a better superhero.

Penny asks Leonard to lie to her father (Keith Carradine); Howard, Raj and Bernadette pull an all-nighter at a telescope.