Edward Norton says he decided not to reprise the role of Hulk due to the commitments a franchise like that demands of an actor.
Norton played Bruce Banner for the first time in 2008, when The Incredible Hulk hit the big screen directed by Louis Leterrier.
The end of the movie saw Robert Downey Jr make an appearance as Tony Stark and reveal that the Avengers were being put together. However, Norton did not return in Avengers Assemble, and saw Mark Ruffalo take over the role.
Norton has talked about the role and has revealed why he walked away from the franchise - he admits that he wanted more 'diversity' in his roles.
Speaking to National Public Radio, the actor said: "My feeling was that I experimented and experienced what I wanted to. I really, really enjoyed it.
"And yet I looked at the balance of time in life that one spends not only making those sorts of films, but then especially putting them out and obligations that rightly come with that.
"And there were just a lot of things that... I wanted more diversity. I sort of chose to continue on my path of having a diversity of experiences."
Avengers Assemble went on to hit the big screen in 2012, and gross over $1 billion at the global box office: it is the third highest grossing movie of all time.
However, Norton is set to return to the big screen in Birdman, which has already been met with critical acclaim on the festival circuit.
Birdman sees Norton work with director Alejandro González Iñárritu for the first time, and could find himself in with the chance of picking up an Oscar nomination at the beginning of next year.
Michael Keaton, Zach Galifianakis, Emma Stone, Naomi Watts, and Andrea Riseborough all join Norton on a very impressive and exciting cast list.
Birdman is released 2nd January 2015.
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