 "Two Guys Naked in a Hot Tub" features the first major appearance of Butters Stotch, who became a main character in the series in later seasons; prior to this episode, he was a nameless background character, having had a non-speaking background role in Cartman Gets an Anal Probe.They based Butters on the show's animation director, Eric Stough, whom they mocked while working on the film.