Curt Connors created an enervator to help remove the Lizard condition that was in his system and tested it on an Iguana. Unfortunately the Iguana became mutated and turned into a creature with the memories of the Lizard. The Iguana then fought Spider-Man and the Lizard until both he and the Lizard fought Spider-Man together.
He was defeated when Spider-Man used a portable Enervator to increase his power while decreasing the Lizards. With his power over increased it seemed as if the Iguana exploded but in reality he was transformed back into his original form.
Iguana somehow resurfaced years later. In the reptile house of the Central Park Zoo, Spider-Man fought Iguana and various crocodiles. Iguana tried to hypnotize Spider-Man but his special lenses didn't allow it. He then tackled Spider-Man out of the reptile house and Peter got a call from his Aunt May. May told Peter she hadn't seen him in days and asked him if he and Anna Maria Marconi were coming to dinner, making him realize she still thought they were dating. Peter then got a call from Anna much to Iguana's annoyance. Despite the call, Spider-Man managed to defeat Iguana and webbed him up.
The Iguana had all of Curt Connors' memories and the Lizard's powers with none of Curt's humanity. He could hypnotize humans, scale walls, command other reptiles, use his claws and prehensile tail as weapons and was bulletproof, but was extremely light and temperature-sensitive.