Williams was born with Achondroplasia, a type of dwarfism. His condition plays a large part in the bits in both his stand-up comedy and television roles. He was a student at the University of Southern California but dropped out to pursue his acting and comedy career.
Williams got his start by attending a Carlos Mencia live comedy show. While he was in the crowd Mencia made jokes about dwarfs. The people sitting close to Williams were scared to laugh. Mencia noticed this, then noticed Williams and he asked Brad to join him on stage. Brad cracked a few jokes and impressed Mencia. Mencia then asked Williams to try stand-up and be his opening act on the road. Brad has been Mencia's opening act ever since, opening up shows on both the Mind of Mencia tour and the popular Punisher Tour.
Brad's memorable roles on the Mind of Mencia include playing a dwarf whore ("whorf"), the leader of an all dwarf basketball team, joining Mencia at a Renaissance faire, and giving a speech about his hatred of podiums. Brad is frequently confused with Wee Man from Jackass because of their similar appearance. For St. Patrick's Day 2008, Brad, dressed as a leprechaun, made an appearance on the Tonight Show with Jay Leno.