Unlike all of the other cross-species, which were created after Curt Connors terrorized the city as the Lizard, Rhino was the result of a pet project of Connors' direct superior, Rajit Ratha. As Connors and Peter Parker worked to develop the serum that would ultimately turn Connors into the Lizard, Ratha applied what he had learned through Connors' research to black-market dealings. Without the knowledge or consent of his superiors at Oscorp, Ratha forcefully enlisted the help of Michael Morbius, threatening to end the reclusive biochemist's career if he refused to help. Morbius reluctantly complied, applying the rhinoceros DNA with which Ratha supplied him to a cross-species serum similar in nature to Connors' own for the Lizard.