- "I'm the old Dinobot. I dont want anyone to know about my old name. But you know it! I must destroy you!!!! "
Mega-Rex is the original Dinobot reborn as a Ty-rex, ant, and snake Fuzor. In this new, heavily-armed and flight-capable form, he now rivals even Megatron in size. In addition to a shield, he carries two primary handheld weapons, plus a third that contains venom "snake." With this improved body, he has also upgraded his allegiance, having sworn eternal loyalty to Megatron. Be careful, however. He guards the secret of his original form fiercely, and a new head design leaves no hints that he used to be the honorable Dinobot.
Some time after the the body of Dinobot was destroyed WITH HONOR!, Megatron ordered Inferno and Death Blade to investigate a steses pod in sector 5.6 by 7.7. When they arrived, the pod had alread began to scan a new form for itself. Mixing the DNA of a Ty-rex, a snake, and an ant, Mega-Rex emerged. Fearing the new protoform was a Maximal, Death Blade attacked while Inferno returned to base to inform Megatron. Death Blade was sadly no match for the powerful new Mega-Rex, and when Mega-Rex let slip that he was originally Dinobot, he killed Death Blade to keep others from knowing.
Despite being born a Maximal, Mega-Rex swore loyalty to Megatron, which Megatron accepted, though with reservations. Meanwhile, Terrorsaur and Scorponok had sworn vengeance against Megatron, so Megatron ordered Mega-Rex, Buzzaw, and Inferno to find them in secor 5. When they were found, the two renegades decided to turn on each other. With Terrorsaur unconscious, Buzzaw fired his missiles at Scorponok, obliterating him. Scorponok did not exist any more. Mega-Rex was furious; Megatron ordered them to bring the two back alive. Buzzaw laughed, and Mega-Rex began to fight him. Even though Buzzaw had the advantage, Mega-Rex took the advantage from him, allowing Mega-Rex to destroy him. Mega-Rex turned at Terrorsaur, who reacted with fright.
With Terrosaur imprisoned, Mega-Rex demanded they free him and, with their combined might, attack and destroy the Maximals. Megatron wanted Tarantulas to finish his secret weapon first, however. Once that was completed, they orchestrated an attack on the Maximal base. Mega-Rex and Blackarachnia attempted to break into the Axalon, while Tarantulas and the others attacked outside. Blackarachnia attempted to hack the Maximals' shield, but Mega-Rex grew impatient. He pushed Blackarachnia aside and, since he was formerly Dinobot, easily entered the code to open the shield. This made Blackarachnia suspicious.