Curt Connors lost his arm in an accident and decided to use himself as a guinea pig in his own experiment using his Neogenic Recombinator to grow his arm back. It was successful at first, but he mutated into a giant Lizard creature and clashed with Spider-Man in an attempt to turn all of humanity into Lizards like himself. He failed and was turned back into Dr. Curt Connors; however, under extreme stress or anger, he would turn back into the monstrous creature known as the Lizard.