As a result, Parker and Stone broke off relations with FOX and took the series somewhere else. They pitched the series to MTV and Comedy Central, and decided it was best suited for the latter, fearing the former could turn it to a more kid-friendly show later on. Comedy Central agreed to pick up the series, and the premiere episode, "Cartman Gets an Anal Probe", debuted on the network on August 13, 1997, while Mr. Hankey would debut in the tenth episode, "Mr. Hankey, the Christmas Poo". In tradition with the show's cutout animation style, the characters are composed of simple geometrical shapes and uninflected patches of predominantly primary colors. They are not offered the same free range of motion associated with hand-drawn characters, as they are mostly shown from only one angle, and their movements are animated in an intentionally jerky fashion. Ever since the show's second episode, "Weight Gain 4000", all the characters on the show have been animated with computer software, though they are portrayed to give the impression that the show still utilizes the original technique of cutout animation. Stone and Parker voice most of the male "South Park" characters. Mary Kay Bergman voiced the majority of the female characters until her death in 1999, near the end of the third season. Eliza Schneider and Mona Marshall succeeded Bergman in 1999, and respectively 2000, with Schneider leaving the show in 2003, after the seventh season. 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 characters. Stewart was originally credited under the name Gracie Lazar, while Schneider was sometimes credited under her rock opera performance pseudonym Blue Girl. Some "South Park" staff members voice other recurring characters; supervising producer Jennifer Howell voices student Bebe Stevens, 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. "South Park" producer and storyboard artist Adrien Beard, who voices Token Black, the only African-American child in "South Park", was recruited to voice the character "because he was the only black guy [in the] building" when Parker needed to quickly find someone to voice the character during the production of the season four (2000) episode "Cartman's Silly Hate Crime 2000".