Lizard

The Lizard (Dr. Curtis "Curt" Connors) is a character appearing in American comic books published by Marvel Comics. Created by Stan Lee and Steve Ditko, he first appeared in The Amazing Spider-Man #6 (November 1963) as an enemy of the superhero Spider-Man. While the character has retained this role throughout most of his subsequent appearances, he has also been portrayed as a tragic antihero and occasional ally of Spider-Man. Connors is sometimes an ally of Spider-Man just as himself, and not necessarily as his alter ego.

In the original Earth-616 version of the story, Curt Connors was a geneticist researching the ability of certain reptiles to regrow missing limbs. He developed a lizard DNA-based serum that would allow humans to do the same, and tested it on himself, hoping to regain his missing right arm; instead, he transformed into a feral anthropomorphic lizard. Although Spider-Man was able to undo the transformation, the Lizard remained a part of Connors's subconscious and would resurface time and time again, often retaining Connors's intelligence and attempting to replace humankind with a race of reptilian creatures like himself. Many stories featuring the Lizard deal with the effects he has on Connors's life and psyche since the latter lives in constant fear that the Lizard will one day completely and irreversibly take over his body. Because of this, he works tirelessly to find a permanent cure for his alternate personality, much to the worry of his wife, Martha Connors, and son, Billy, but also standing in contrast to other Spider-Man foes who take pride in their powers and use them irresponsibly.