In 1985's Incredible Hulk #312, longtime Hulk scribe Bill Mantlo told an origin story that established it was more than gamma radiation that created the Hulk. A young Bruce Banner endured horrible abuse from his father, and the Hulk was, in part, a manifestation of that trauma. Peter David later expanded upon this idea during his time on Incredible Hulk, establishing that the trauma created multiple Hulk personalities. Other writers added to this idea, including Paul Jenkins, who showed Banner had dozens of splintered Hulk personas.
The most recognizable is the Savage Hulk — the green, monosyllabic Hulk known for catch phrases like "HULK SMASH!" There is the gray Joe Fixit Hulk, who is intelligent, cunning, and sadistic, but not as powerful as other Hulks. The Professor — a variation of which appears in Avengers: Endgame – believed himself to be a merging of the Hulk's disparate personalities, but proved to be another splinter representing Banner's more rational, intellectual side. There is the so-called Grayvage Hulk — a version with the green skin, power, and myopic rage of the Savage Hulk but the cunning and intelligence of Joe Fixit. There is a massive Hulk representing Banner's guilt, a malevolent Devil Hulk who emerged as the dominant persona in the comic Immortal Hulk. There is even Savage Banner — the Savage Hulk personality, but in the body of Bruce Banner.
