Norton Wearing Multiple Hats for The Incredible Hulk
Star smash script! Puny screenwriters!
According to the article, Penn was indeed hired to write Incredible Hulk's script -- and did just that, writing three drafts in a year. By this spring, however, Penn needed to move on to other projects, and both the studio and director Louis Leterrier felt they were missing their final draft. Fortunately, their just-signed star had the experience, the background, and the desire to step in. From the article:
When Norton came in to meet about starring as Banner in April, the film had already been greenlighted and there were just three months before shooting was scheduled to begin, just after Independence Day. But Norton had well-established (if underground) writing experience and strong ideas about how to separate the film from any confusion over its connection to the 2003 Ang Lee version by casting it in a more distinct, starting-over vein like "Batman Begins" or "Casino Royale."
So Norton's initial deal included payment not just for his acting services but for his writing talents too, with his draft contractually stipulated to be turned around in less than a month. As it turned out, Norton delayed work on another screenplay job to do "Hulk," and he continues to tweak the script as principal photography hits its halfway point outside Toronto.
So there you have it. And don't cry for Penn, by the way. He's working on scripts for The Avengers and a possible X-Men spinoff.
Source: LA Times