 While he originally voiced Tweek without any computer manipulation, Stone now does so by speaking within his normal vocal range and then adding a childlike inflection.The recorded audio is edited with Pro Tools, and the pitch altered to make the voice sound more like that of a fourth grader.Tweek is introduced in the season two (1998) episode "Gnomes" and is as prominent as one of the four main characters through the middle portion of the sixth season (2002).