The X-Men star discovered his sister could do anything he could during the making of X-MEN 2.
He says, "My sister came to visit and people have always said we look kind of alike, so my make up lady took her off to the make up trailer and apparently they got carried away, she put on the wig, the mutton chops, the costume. And we really did look the same!
"So I got her to do one of my takes without telling anyone. And Bryan Singer, the director, is going "Come on Hugh!" you know, thinking I've forgotten the next thing to do.
"I mean for 40 seconds there were 15 people watching her on the monitors and not one of them realised it wasn't me. They thought I was making some weird acting choices. You could call it a practical joke but for me it was horrifying."