King Leonardo's main arch-enemy is the gangster-visaged Biggie Rat (voiced by Jackson Beck impersonating Edward G. Robinson), who routinely attempts to overthrow Leonardo and take over Bongo Congo for himself with the help of Leonardo's dimwitted sibling Itchy Brother (voiced by Allen Swift). Biggie is often also assisted by an evil German inventor named Professor Messer (voiced by Jackson Beck) or Odie's flirtatious sister Carlotta. Biggie and Itchy's various schemes always end with them either landing in the dungeon or getting away.