Leary was born and raised in Worcester, Mass. He attended Emerson College in Boston, where he founded the Emerson Comedy Workshop. He holds an honorary doctorate from the school.
He started attracting interest in the 1990s for his rapid-fire monologues on MTV and his standup comedy recordings.
Leary has acted in several movies, including "Wag The Dog" and "Demolition Man," and has voiced characters for the animated films "Ice Age" and "A Bug's Life.
He also created the Fund for New York's Bravest to help the families of firefighters who died on Sept. 11, 2001