Parker and Stone voice most of the male South Park characters Mary Kay Bergman voiced the majority of the female characters until her suicide on November 11, 1999. Mona Marshall and Eliza Schneider succeeded Bergman, with Schneider leaving the show after its seventh season (2003). She was replaced by April Stewart, who, along with Marshall, continues to voice most of the female characters. Bergman was originally listed in the credits under the alias Shannen Cassidy to protect her reputation as the voice of several Disney and other kid-friendly characters Stewart was originally credited under the name Gracie Lazar, while Schneider was sometimes credited under her rock opera performance pseudonym Blue Girl.  Other voice actors and members of South Park's production staff have voiced minor characters for various episodes, while a few staff members voice recurring characters; supervising producer Jennifer Howell voices student Bebe Stevens, co-producer and storyboard artist Adrien Beard voices the school's only black student, Token Black, writing consultant Vernon Chatman voices an anthropomorphic towel named Towelie,and production supervisor John Hansen voices Mr. Slave, the former gay lover of Mr. Garrison. Throughout the show's run, the voices for toddler and kindergarten characters have been provided by various small children of the show's production staff.
When voicing child characters, the voice actors speak within their normal vocal range while adding a child-like inflection. The recorded audio is then edited with ProTools and the pitch is altered to make the voice sound more like that of a fourth grader.
Isaac Hayes voiced the character of Chef. Hayes, who lived and hosted a radio show in New York during his tenure with South Park, would record his dialogue on a digital audio tape while a respective episode's director would give directions over the phone, then the tape would be shipped to the show's production studio in California. After Hayes left the show in early 2006, the character of Chef waskilled off in the season 10 (2006) premiere, the return of chef