Mary Kay Bergman (June 5, 1961 – November 11, 1999), also briefly credited as Shannen Cassidy, was an American voice actress and voice-over teacher.

After acting in her first professional role in the television film Return Engagement, she studied theater arts at UCLA for three years.

Struggling to find a job suited for her, she was trained under her voice-acting teacher Kat Lehman and started performing radio voiceovers.

Bergman was cast as nearly every female character in South Park after she gave Trey Parker and Matt Stone ideas they originally did not have.

[3][4][5] An only child,[6] her mother, Patricia McGowen,[7] was a cel painter for Max Fleischer on Popeye cartoons in New York City.

[3] Bergman's early passion for impersonating was influenced by Snow White and the Seven Dwarfs, a film she watched in theaters at the age of six or seven.

[8] At age 16, Bergman received her first professional acting job in the television film Return Engagement, which starred Elizabeth Taylor.

[10] Upon graduating from Hollywood High School in June 1978 with top academic honors,[citation needed] Bergman enrolled at UCLA and studied theater arts from 1978 until 1981.

[13] Bergman also worked as a receptionist for an insurance company and from there she moved up the ranks to become an assistant underwriter, which she found "extremely boring.

"[14] Her first voice role was a frightened woman in a radio commercial for a small home security company on a local station in 1986.

[14] Bergman was chosen by former Disney executive Les Perkins after a "long and tedious search" of talent agencies and voiceover classes throughout Los Angeles.

[16] She began doing matches for other actors such as Jodie Foster, Gillian Anderson, Helen Hunt, Julia Roberts, Jennifer Tilly, Emma Thompson, and Alfre Woodard.

[20] When Disney was working on a restored version of Snow White and the Seven Dwarfs on LaserDisc, Caselotti was brought back in to record a rediscovered scene that was missing its audio track.

[16] Disney received hundreds of complaints after the ceremony, noting the changes to the Snow White character that Jeffrey Katzenberg had made, including a more modernized look to match her updated voice.

[16] Katzenberg issued written apologies, and Bergman did not publicly admit to voicing Snow White while Caselotti was still alive.

[11][12] Trey Parker and Matt Stone were looking for a different voice actress for the female characters in South Park, as they were unhappy with Karri Turner's performance in the series' unaired pilot.

[17] The ideas she gave included portraying Liane Cartman as a "1950s sitcom-style mother", interjecting Sheila Broflovski's catchphrase "What, what, what!"

In her interview with Entertainment Weekly in 1999, Bergman credited South Park for distancing her out of her reputation known for voicing characters in children's animation.

[22] After South Park became a success, however, Shannen Cassidy began to receive copious amounts of fan mail and Bergman decided to abandon the alias.

[22] Bergman was nominated for Outstanding Individual Achievement for Voice Acting in an Animated Feature Production for her performance as Sheila Broflovski at the 27th Annie Awards.

[23] South Park creators Trey Parker and Matt Stone were initially "too distraught" to issue a statement about her death.

[23] On March 2, 2000, during an interview with Parker and Stone at the Paley Center for Media, they issued a statement about Bergman, stating they realized that "one person wasn't going to do it" because of her vocal capabilities, and that they were in a process of finding "a lot of talented voice people".

[3] Bergman cited it as an inspiration to crossover from a mere fan to a performer, stating that the film "made a complete impression" on her.

[3] Shortly thereafter, Bergman began impersonating everything, including Lily Tomlin on Rowan & Martin's Laugh-In and her neighbor's barking dogs.