Penny is dating Zack again and becomes upset when the guys make fun of him, making him feel stupid. When they go over to Penny's to apologize to him, they realize he can help them out with the New Year's costume competition at the comic book store and offer to make him Superman in their Justice League. Unhappy that he's been usurped, Leonard calls dibs on being The Green Lantern which forces Koothrappali, much to his dismay, to dress up as Aquaman. Zack signs Penny up to be Wonder Woman but she refuses to wear the dark wig. When Zack sides with the guys that she should wear it, she gets upset and tells the guys she's not going to the party at all. After failed attempts by Zack and Sheldon, Leonard goes over to Penny's to try and make amends and get her to come with them. They share a nice moment and at the party, the gang ends up winning the costume contest.