Will Smith almost played Neo, Michelle Pfeiffer almost played Clarice Starling in The Silence of the Lambs, and Josh Brolin was considered for the role of Miles Quaritch in the Avatar franchise, which is currently played by Stephen Lang.
It's easy to see how the gruff Brolin could have made his presence known as Quaritch, but it simply wasn't to be. Speaking to Josh Horowitz, Brolin said it was a difficult decision, but the time commitment was what turned him away.
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Putting himself into one role for a year and a half simply seemed too much of a commitment for Brolin. Comparing the role to his appearance in the MCU as Thanos, he said that he would only appear occasionally as the purple alien.
"It was Stephen Lang," Brolin said, clarifying it was a role in the first Avatar movie he turned down. "Who I knew, and I was very happy for him. He was amazing, so it happened exactly how it should've."