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 '' '' .
Scott Vincent James Baio ( born September 22 , 1960 in Brooklyn , New York ) is an American movie and television actor and television director . He is best known for his roles as Chachi Arcola on the sitcom `` Happy Days '' and its spin-off , `` Joanie Loves Chachi '' , and as the main character in the series `` Charles in Charge '' .