Sullivan served as the recurring character Dabney Hooper on Malcolm in the Middle from 2000 to 2003. Sullivan has also lent his voice to the characters Danny O'Farrell and Everitt Konquist on the Disney animated series Fillmore! Sullivan has guest starred on television programs such as The Secret World of Alex Mack, Seinfeld, The Amanda Show, NewsRadio, Chicago Hope, Mad About You, ER, Scrubs, and Max Keeble's Big Move.
