When The Avengers was still brewing, a massive question mark lingered over what to do with the Hulk. The character's presence in an Avengers movie was a foregone conclusion, but uncertainty surrounded who would be portraying the character.
Edward Norton had portrayed Hulk's alter-ego, Bruce Banner, in The Incredible Hulk, and the appearance of Robert Downey Jr.'s Tony Stark in the film teed up the idea of Norton joining the movie version of the Avengers. However, Norton and Marvel Studios came to blows in post-production of The Incredible Hulk — possibly over creative control, money, or both, depending who you ask – complicating the concept of Norton reprising the role. Despite those difficulties, Norton stated that he was open to returning to the role in The Avengers in the fall of 2009.
He would never get the chance, though, as Marvel Studios announced in July 2010 that a new actor would be going green in The Avengers. “Our decision is definitely not one based on monetary factors,” Kevin Feige said at the time, “but instead rooted in the need for an actor who embodies the creativity and collaborative spirit of our other talented cast members.”
While this indicated that Marvel made the call regarding Hulk's recasting, Norton would claim years later that he had consciously chosen not to reprise the role out of fears of limiting his options as a performer.