“One of the true surprises for me during the making of Fight Club was Brad Pitt. He never showed any evidence of an actor who was out there trying to protect his 'Brad Pitt–ness.' Usually when this happens to a young actor, the first instinct is hang on and play it safe. He doesn't want to fuck things up. And for sure, his manager, agent, and lawyer don't want to fuck things up. An awful lot of money is at stake. The result is that actors tend to repeat the same performances and the same kind of roles that created the most success. Without a shred of false vanity or the use of old tricks to win over an audience, Pitt proved to be a formidable actor of enormous talent. Can anyone imagine, thirty years ago, Robert Redford or Warren Beatty shaving his head or working without caps on his teeth or exposing himself so raw and ruthless as Brad had done and just let the chips fall?”

-- Producer Art Linson in his book, “What Just Happened? Bitter Hollywood Tales from the Front Line.” His take on how stunned the execs were when they screened “Fight Club” is great, but not as great as the battle over Alec Baldwin's beard. 

As for Pitt, agreed. Cf., this piece from 2005.