Gamma-powered psychiatrist Leonard "Doc" Samson captured the Hulk and successfully separated Banner and his alter ego. Without Banner's psyche to restrain him, the Hulk became a greater danger than ever before. Realizing there was only one way to reign in the Hulk, Banner agreed to merge with the monster. But the stress of the re-integration fractured Banner's subconscious, creating the street-smart gray Hulk. During this time, he spent several years in Las Vegas, sometimes operating as an enforcer calling himself Mr. Fixit (or "Joe Fixit.") The smart-mouth Fixit was an ill-tempered, wise-cracking, thuggish brute whose personality resembled that of his father and the fraternity boys who surrounded him in college. It was also at this time that Joe Fixit began his a short-lived relationship with the future wife of Rick Jones, Marlo Chandler. In this state of the Hulk, Banner again found himself changing into the Hulk at night and into his human form in the light of the day.

Soon after, the swirling mess of persona and mentalities took their toll on the ever-flustered mind of Dr. Banner, and a battle for supremacy and control took place in Banner's subconscious. With assistance by the Ringmaster and his hypnotic abilities, Doc Samson tapped into the subconscious of Banner and reached his separate incarnations. Through this hypnosis, Banner, the green Hulk, and the grey Fixit all aligned to face their true inner demons-- Banner's unresolved issues with his abusive father and the murderer of his mother. With this realization, Banner was able to fuse these mentalities together, finding peace of mind. However, a green but intelligent version of the Hulk emerged. He had the mentality of Dr. Banner but the body and abilities of the Hulk – later nicknamed the Professor. Although Banner had his dominant personalities merged together, there were a number of other personas running through his mind including that of a "Devil-Hulk."