Birdman, the impressively starry film about Cash Money Records CEO Bryan “Birdman†Williams about Michael Keaton, Emma Stone, Naomi Watts and Zach Galifianakis all being in a movie together, has brought Edward Norton aboard. He’ll play a bigheaded actor toplining a theatrical production based on a famous superhero role Keaton’s movie star character pioneered. The dark comedy will come from Alejandro González Iñárritu (21 Grams, Biutiful).