Henry Philip "Hank" McCoy was born in Dundee, Illinois, in the United States, to Norton and Edna McCoy. His father, Norton McCoy, is employed at a local nuclear power plant before Henry's birth and was once exposed to intense nuclear radiation, which appears to have caused his son's mutation. Hank is born with a vast intellect, unusually long arms and legs, and unusually large hands and feet for a human
Shortly after his twentieth birthday, Hamk becomes a research scientist at the Brand Corporation, a genetics research facility. His assistant, Linda Donaldson, quickly becomes his girlfriend. Hank isolates a "hormonal extract" allowing anyone to become a mutant for a short period of time, and uses the mutagenic serum on himself to disguise his appearance while foiling an attempt to steal his research. However, he waits too long to reverse the process, leaving him permanently transformed. He has grown grey fur (which later turns blue) all over his body and acquired pointed ears, elongated canine teeth, claws, the ability to run on walls and ceilings like a spider, enhanced senses, an accelerated healing factor, and a feral side he struggles to control.
After being critically wounded. Hank's body undergoes a secondary mutation, jump started by Sage. The result is a more feline appearance equivalent to that of a big cat. His strength, speed, stamina, sturdiness, and senses increase further with this change. He gains cat-like agility, flexibility, coordination, and balance, and all his senses are enhanced to twenty times that of a normal human being. In addition, Beast develops an accelerated healing factor that allows him to repair mild to moderate injuries within the span of a few hours. However, as his hands and feet change from simian to feline (going from a normal human set of four fingers to just three, retaining the opposable thumb), he loses his superhuman dexterity, once admitting that he used to play the guitar, but is now learning to play the drums instead. Following the X-Men's relocation to San Francisco, Beast discovers that he had regained some of his old manual dexterity.
- Hank McCoy first appeared in "The Halloween Door II"