In 1993, Bryan Callen moved to Los Angeles where he was discovered in a comedy club by producers who were looking for talent for a late night sketch show called MADtv. As of March 2006, Callen currently lives in Venice, California.

Callen was one of the original nine cast members of MADtv when the series aired in 1995. Nearly every week, he would introduce audiences to strange but funny characters. Callen's most popular characters included monkey-brained Pool Boy from the Cabana Chat with Dixie Wetworth sketches, motivational speaker Al Casdy, frustrated Linder son Mark Linder "relationship challenged" death row inmate, Jeremy Anderson.

He also was noted for his celebrity impressions. Before Pat Kilbane or Will Sasso joined the cast, he impersonated Al Gore, Bill Clinton, Luke Perry, Robert De Niro, and Steven Seagal. Callen's impersonation of Bill Clinton was well known in a parody of the 1996 U.S. Presidential Election debate where he faced off against the new and improved U.S. Senator Bob Dole who reinvented himself into "Bob Dolemite" in order to win over the youth vote.