A young Rex demonstrated the use of a giant bio-mechanical form that appeared to have most of Rex's current capabilities, including a version of the B.F.S. on one arm, Punk Busters for legs, Slam Cannons on both shoulders, and a Smack Hand on the other arm. It also seemed to have a a chest plate that slightly resembled the Smack Hands, shoulder pads that resembled the turbines of the Boogie Pack, and the Helmet from when he uses the Rex Ride. While in this large and imposing form, he demonstrated typical E.V.O.-on-the-loose behavior, and after reverting to his human form, he lost his memories. Rex partially transformed into this form when he was about to be dissected by Dr. Fell, meaning this may be a defense mechanism. He was also about to return to this form when he was trying to regain his memory with Caesar's ineffective machine.