The star reveals his father was a keen photographer while he was growing up and he was always taking shots of the most mundane things - like meatloaf - and so one day, young Ryan decided to play a joke on his old man after stealing his camera during a family dinner.

The Proposal star recalls, "I grabbed the camera and I went in the bathroom and I just took a picture of my penis. I just wanted to see if he would naturally edit these photos at some point. No! He emailed it out.

"So one day, I hope it doesn't happen, but there's a penis picture of mine floating around somewhere."

And, unlike other celebrities who have been caught with their pants down, 'sexting' penis pictures to girlfriends, Reynolds can't imagine the idea of receiving a vulgar photo is one that turns on women - or men.

Appearing on U.S. TV chat show Conan, he adds, "I can't think of anything more threatening to send a woman than a picture of a penis. In terms of sexy, it's, like, just a rung below a picture of yourself committing domestic terrorism."