First, the entire show was based off of a scared girl's life before she died, this girl was named Angelica. Yes, Angelica. All of the character in the show were based off of real people in Angelica's life. But you see, the show was entirely a figment of Angelica's imagination. She imaged all of this.http://www.fanficsgalore.org/viewtopic.php?f=275&t=1893
The story behind Rugrats is common life experiences involving kids. The movie shows on how was the kids' day to day live, and the adventures in their imaginations. The thing about angelica is only true in the movie and not in real life.