The Bus Pants Utilization
Leonard's idea for a smartphone app derails his friendship with Sheldon.
The Justice League Recombination
The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.
The Alien Parasite Hypothesis
Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.
The Boyfriend Complexity
Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope.
The 21-Second Excitation
While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party.
The Apology Insufficiency
Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy.
The Irish Pub Formulation
Leonard keeps an affair a secret from Sheldon, Howard and Raj.
The Desperation Emanation
Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.
The Hot Troll Deviation
An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.
The Zazzy Substitution
The guys are concerned as Sheldon searches for an alternative to human companionship.