S.U.B is (as her name implies) a talking robotic submarine and a one-time villain who only appears in the episode C.H.O.P. She was supposed to appear in Lance Chestwax's upcoming show with her name as the title, but when C.H.O.P discovered that, her sensors targeted him and she tried everything to destroy him, prompting Robotboy to protect C.H.O.P. She was eventually defeated by Robotboy.