Before his father used the lizard serum on himself, Billy was reading up on lizards. When Martha realized that Curt's lizard DNA formula (originally designed to recreate his lost right arm) was starting to take over him, she sended him off to the other room to prevent him from finding out, but Billy ended up witnessing his father's transformation into the Lizard anyway. Worried that his dad's transformation would make him forget about him, Billy follows the Lizard, Eddie, and Spider-Man to the zoo where he tries to appeal to the human in him. Although this tactic didn't work, it provided Spider-Man the necessary distraction to force feed the Lizard the gene cleanser that changed him back to Curt Connors.
The next year, Billy moves with his family to Florida, as Miles Warren had taken over the ESU lab by blackmailing Curt with the knowledge that he had been the Lizard.