The Justice League Recombination (2010)

The guys discover that Penny and her ex boyfriend, Zack, are back together and they take advantage of his lack of intelligence and make fun of him. After Zack finally realizes what's going on and storms out, the guys decide to apologize to him. Upon receiving Milk Duds, Zack immediately forgives Leonard and his friends and goes to the comic book store with the guys, ditching Penny in doing so. At the store, the guys realize that Zack would be a great Superman for their Justice League group costume at the upcoming New Year's Eve costume party at the comic book store, as he is taller and more muscular than Leonard. They return home with comic books and a Wonder Woman costume for Penny. She initially refuses to go to the party, but as no other girl is available to go, she finally agrees. The night of the party arrives with Howard being dressed as Batman, Raj as Aquaman , Sheldon as The Flash, Leonard as the Green Lantern, Zack as Superman and Penny as Wonder Woman. Just before they are about to go, Sheldon points out that Penny should wear a black wig, as Wonder Woman isn't blonde. However, Penny rejects to wear the wig and eventually refuses to go to completely. None of the guys, not even Zack, can convince Penny to go. Since Zack doesn't want to go without Penny and the Justice League isn't complete without Superman, Sheldon suggests they change their costumes to characters from the Muppet Babies. Finally, Leonard talks to Penny and she reveals that she only got back together with Zack because she didn't want to be alone for New Year's Eve. It is implied that she still has feelings for Leonard. Penny suddenly agrees, puts the wig on, and the group later wins the costume contest. When midnight strikes, Zack kisses Penny with her looking guiltily at Leonard. The episode concludes with the group witnessing an ongoing car theft on the way back home and despite wearing Justice League costumes, they comically scurry off, none of them, not even Zack, brave enough to stop the car theft.

Recurring characters: Brian Thomas Smith as Zack Johnson.

Title reference: Sheldon, Leonard, Howard and Raj inviting Penny and Zack to be Wonder Woman and Superman in their Justice League team.