G-9 (voiced by Maurice LaMarche) is Gadget Boy's robotic canine companion. He can transform into anything Gadget Boy and his friends need and assists Gadget Boy to get him and Agent Heather out of the stickiest situations He is the series' counterpart to Brain. Gadget Boy and G-9 appear to switch between being fully robotic to being half robotic in different episodes. Although he is a robot dog, in "The Power of Babble" he is revealed to be a half robot when he is affected by the Babbilizer Ray enabling him to speak in an old English, intelligent accent. Unlike Brain, G-9 is usually seen with Gadget Boy, and Gadget Boy does not mistake him for being an enemy agent, as opposed to when Inspector Gadget will usually mistake Brain for being a M.A.D. agent.