Sullivan has voiced Shego on Kim Possible, Joan of Arc on Clone High, and Mira Nova in Buzz Lightyear of Star Command. She also starred in a pilot called Me and My Needs that was declined by ABC. She has also appeared on King of Queens as a reoccuring supporting actor.

Nicole Sullivan was born to Ed and Madonna Sullivan of Manhattan (no relation to Ed Sullivan). She took dance classes at the age of seven, and performed on and off Broadway with the First All-Children’s Theatre. Madonna, an antiques dealer, and Ed, a New York State assemblyman, wanted to raise Nicole and her sister Jennifer in a quieter environment, and moved the family to rural Middleburgh, New York in 1982. After graduating as Middleburgh High School’s class valedictorian in 1987, Nicole attended Northwestern University as a theatre major. She studied William Shakespeare, Harold Pinter, Anton Chekov, Henrik Ibsen, and Greek tragedies, all the while working two jobs to pay her way through college and writing plays and sketches for the student theatre. Nicole spent her junior year in London studying at the British American Drama Academy and became a member of the Greenwich Shakespeare Company. Nicole graduated Northwestern with honors, then moved to Los Angeles to inexplicably, considering her background, write for, and perform in, comedy clubs and at theatres with improv and sketch comedy troupes before getting sporadic guest starring roles and becoming the breakout star of MADtv.