The Wheaton Recurrence

Summary
One night after making love, Leonard surprises Penny by saying "I Love You" but she can only say "thank you" and they both start to think about where their relationship is heading. The next day, Penny and the guys are in a bowling match with Stuart and the gang from the comic book store, and since one of their teammates couldn't come they got Wil Wheaton to substitute. Sheldon vows to get revenge for what happened in The Creepy Candy Coating Corollary. During the match, Penny and Leonard are eating, at which point Penny says that she loves chili cheese fries. Since she used the word "love" to describe her feelings for the chili cheese fries, this gets Leonard angry, as she could not use that word to describe her feelings for him. They have a fight, and Penny walks out. This causes the gang to forfeit the bowling game. Sheldon, very distraught that they had to forfeit, gets Leonard and Penny to talk and supposedly patch things up. They go back to the alley where Sheldon and Wil both try to beat each other in the game. Sheldon's team, the "Wesley Crushers" (in reference to Wheaton's character on Star Trek) needs one strike to win or they lose a bet.Wil talks to Penny and tells her that he endured two years of misery with a girlfriend who could not say "I love you" to him. It's Penny's turn to bowl, but she storms out again after Leonard pressures her as she realizes that she will never be able to say "I love you" to him. Leonard realizes it's all over between him and Penny, and so is the game since they had to forfeit again. After the game, Sheldon confronts Wheaton for what he said to Penny, and Wheaton reveals that he intentionally broke up Leonard and Penny so that they would forfeit the match. The episode folds with the four guys walking into the comic book store dressed like Catwoman, Batgirl, Wonder Woman, and Supergirl, since they lost the bet to Wheaton and Stuart.

Title reference: Wil Wheaton's return as a guest star on the show.