Scott Vincent James Baio (; born September 22, 1960) is an American actor and television director, best known for his roles as Chachi Arcola on the sitcom Happy Days and its spin-off Joanie Loves Chachi, the titular character on the sitcom Charles in Charge, the main character in the musical Bugsy Malone, and for his role as Dr. Jack Stewart in the medical-mystery-comedy-drama series .