The Mamma Mia! star's head was planted on a much bigger man's body for the provocative naked shot used on billboards for The Devil's Double, in which Cooper plays both Saddam Hussein's sadistic son Uday and an Iraqi man who was forced to act as his body double.
The poster features the actor's character, covered in gold and sitting down with his legs wide apart.
But honest Cooper can't have his fans believing that's what he looks like naked.
He explains, ""It's brilliantly hideous, but it's eye catching. There's this bloke in the poster with a really hairy chest and a huge package and that's certainly not me! But it is my head.""