An actor and writer, born in New York, USA in 1969, but he moved to Boston when he was just one year old. He was educated at West Roxbury High School, then attended Northeastern University but did not graduate. O'Neill had a few jobs prior to acting, then moved to Los Angeles, where he started working on radio, television, and film projects in 1992. O'Neill had appeared in many shows, both in acting roles and as himself. Among his most famous works are the films 25th Hour (2002), and Paper Soldiers (2002), as well as the series Arrested Development (2003-2007), and Chappelle's Show (2003-2006). His last screen appearance was in Comedy Central Roast of Charlie Sheen (2011). He was suffering from diabetes, and died of a stroke, on November 29, 2011, at the age of 41.