"Acorn Nuts & Diapey Butts" is a three-part episode of Rugrats that serves as the season finale to the show's sixth season. This episode serves as a lead-in to Rugrats in Paris: The Movie, and it is also notably the last episode to use the original intro sequence, which has been used since the series premiered in 1991. It takes place during the Fall. In this episode, Tommy's fear for changes comes true as Lou permanently moves out of their house and into a retirement home, and must come to terms with his Grandfather not being around as much as before. Meanwhile, Betty tries to find a new love for Chas (none of which turn out great), but Chuckie is starting to feel left out. Phil and Lil on the other hand, have a hard time adjusting to their newly oversized diapers that has been forced upon them, as it becomes very difficult for them to move regularly like they use to. (thetvdb.com)