Los Angeles - Ben Affleck's smile landed him his role in Gone Girl.
The 42-year-old actor stars as Nick Dunne in David Fincher's adaptation of Gillian Flynn's novel and the filmmaker felt the key to finding the right person for the role was getting someone who could successfully play a scene where the writer's sad expression is also perceived as the sinister grin of a man who could murder their wife.
He said: "You cast movies based on critical scenes. In Gone Girl there's a smile the guy has to give when the local press asks him to stand next to a poster of his missing wife.
"I flipped through Google Images and found about 50 shots of Affleck giving that kind of smile in public situations.
"You look at them and know he's trying to make people comfortable in the moment, but by doing that he's making himself vulnerable to people having other perceptions about him."
Check out the trailer ofGone Girl:
"You look at them and know he's trying to make people comfortable in the moment, but by doing that he's making himself vulnerable to people having other perceptions about him."
Fincher has worked with Brad Pitt on several movies, including Fight Club, Se7en and 'The Curious Case of Benjamin Button' and admitted he always offers every leading role on his projects to the World War Z star before anyone else.
He added to Playboy magazine: "It's not because I'm pathetic but because he's good for so many things."