Ben, 42, plays a husband under a cloud of suspicion when his wife (Rosamund Pike) suddenly goes missing in Gone Girl.
It was the "role of a lifetime" for Ben, who has been earning plenty of praise in recent years for his work both in front of the camera and behind it.
But to play Nick Dunne, Ben knew he'd have to throw any vanity out the window - especially when it came to the possibility of nude scenes.
"I think there's some brief nudity in this movie," Ben told MTV News.
"This is a warts and all movie. It can have no vanity. You have to see the naked underbelly of this character."
His on-screen alter ego might be deadly serious, but Ben's not afraid to crack some jokes at his own expense! As he laughingly revealed to MTV's Josh Horowitz, movie-goers might get a little more than they bargained for when they see the film.
"The penis is in there! It costs extra," he joked.
"You've gotta pay fifteen bucks to see it in 3D. It looks better in 3D."
We wonder how Ben's wife Jennifer Garner feels about that!
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