So we asked the film's director, David O. Russell, exactly how much of the film strayed from the actual script.
"To be honest with you," said Russell, "I would argue that it's two-thirds scripted and one-third [improvised]."
But that doesn't mean he let the actors spew dialogue, willy-nilly. "The improvisation is rarely people saying, 'Just go do whatever you're going to do.' It just means that we're rewriting it, making it better in the moment."
While he enjoys letting the actors explore new dialogue, he also seems to have a great respect for the written word. "There are specific lines that never change because they're just good pieces of writing that the actors actually end up defending, like, 'She was the Picasso of passive-aggressive karate.'"
Another great line that didn't change was, "I thought you were mysterious like my mother until I realized mysterious just meant depressed and hard to reach."
So why improvise at all if you have such stunning dialogue? "That aliveness of changing things in the moment is what keeps things feeling immediate and very alive."
Russell claims it's not easy to make a good movie. When we told him it sure looks easy for him, given the success of last year's Silver Linings Playbook, he told us, "No, no, it's very hard."
So what's the recipe for a great film?
"You need great actors who bring you their trust and their hearts, and you have to return that favor by doing everything you can for them to leave all their heart in the movie, all their breath of their character in the movie."
The director continued, "So you write the story and the characters so that you can see Amy go from raw, in curlers, to glamorous and gorgeous, dancing down Park Avenue to intense, emotional, smashing Bradley Cooper over the head with a glass picture frame."
Watch our video to find out what Christian Bale, Jeremy Renner and Amy Adams had to say about going off-script — their answers may surprise you!
American Hustle is currently playing in limited release but opens wide on Dec. 20.
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