LIZARD

In Peter Parker, The Spectacular Spider-Man Vol. 1 #32 (1979), Curt Connors was testing his bio-enervator — a machine built to unlock the secret of how reptiles regrow lost limbs — on a marine iguana in his Empire State University lab. The experiment backfired completely: the device poured part of Connors' own life force, his memories, and the personality and powers of the Lizard into the animal. The iguana rose up as a hulking humanoid reptile — a second Lizard, grown out of a lab animal instead of a man.

The duplicate's first act was to cover its own tracks: it hypnotized Connors into forgetting the accident had ever happened. After that it lived a double life of its own — by day an ordinary iguana, small and silent in its cage; by night a monster stalking the dark on borrowed strength. When it finally stepped into the open, in the reptile house of the Bronx Zoo, it fought Spider-Man while talking with Connors' stolen memories, announcing that it remembered him "from the Connors mammal."

Worse followed in #33–34: the Iguana found the one ally it was built to understand — the true Lizard, Connors himself transformed. Spider-Man rebuilt the enervator into a portable unit and turned it on both reptiles at once, siphoning the Lizard's power out of Connors and dumping the stolen life-energy into the Iguana. Overloaded, the creature burned with more power than any iguana was meant to hold — and disintegrated. Curt Connors went home human, and the world's second Lizard was gone as suddenly as it had arrived.