Season 4, Episode 18 | March 10th, 2011
Wolowitz drives Sheldon crazy as he tries to figure out Howard's magic trick. It seems to work as Howard does it for Raj and Penny and Sheldon spends the rest of the episode coming up with various ways to successfully do the trick himself but to no avail. In the end, we find out that Raj and Penny are in on the joke and Howard's magic trick is simply just a trick on Sheldon - because it's too fun for them when they drive him nuts.
Meanwhile, Priya tells Leonard that she feels uncomfortable with the amount of time that Penny spends hanging around him. She asks him to talk to Penny to let her know that they can't hang out together. Leonard attempts to tell Penny several times but can't seem to get the words out even though he tells Priya that Penny totally understood about the situation and will stay away from them. He's caught in his lie when Penny sees him and Priya out to dinner and tries to join them to kill time before meeting the rest of the gang out for a movie. In the end, Penny figures out what's going on and ends their friendship for him.