Season 2: Episode 41: The One Where Eddie Moves In
Joey and Chandler miss each other terribly but Chandler gets a new roommate, Eddie, after Ross and Rachel encourage him to "move on." Joey decides to ask Chandler if he can move back in but learns that Eddie has replaced him. And a producer has Phoebe record her 'Smelly Cat" song and make a video, but when Phoebe plays it for the gang, they realize it's clearly not Phoebe's voice. When Phoebe eventually figures this out, she feels sorry for the woman who sang because she doesn't get to have a video and Phoebe does. Meanwhile, Ross spends so much time at Rachel's, that he and Monica slip into their childhood bickering.