Title: Cartman's Mom Is a Dirty Slut
Original air date: February 25, 1998

Summary:
"Cartman's Mom Is a Dirty Slut" is the first season finale of the animated television series South Park, and the 13th overall episode of the series. It originally aired on Comedy Central in the United States on February 25, 1998. It is part one of a two-episode story arc, which concluded with "Cartman's Mom Is Still a Dirty Slut". The episode follows Eric Cartman, one of the show's child protagonists, becoming curious about the identity of his father. He discovers that his father is most likely a man his mother had intercourse with during an annual party called "The Drunken Barn Dance". Meanwhile his friends Stan, Kyle and Kenny participate on America's Stupidest Home Videos, after filming Cartman playing in his yard with plush toys.
http://en.wikipedia.org/wiki/List_of_South_Park_episodes