The 45-year-old actor claims he put a lot of work into making sure his body was at it's best for his nude scene in 'X-Men: Days of Future Past', but confessed he didn't get to enjoy watching it back because he'd forgotten to tell his daughter Ava, 8, and son Oscar, 14, to cover their eyes.
He said: "It is actually really cool to watch it [the film] with them until you get to the moment where you're naked onscreen and you forgot to warn you almost 9-year-old daughter.
"And she says, 'Dad, why aren't you wearing underwear?'"
'The Wolverine' star - who is married to actress Deborra-Lee Furness - admits his strict diet on the day of filming the revealing shots may not have been the best idea, as he was so thirsty he passed out.
He told the New York Daily News newspaper: "You have no idea what goes into the lead up to a scene like that. It was a year ago.
"I know that exactly because it was May 21.
"I stopped drinking water for 24 hours, I pumped up on set for about an hour before shooting. And fell asleep by 2 o'clock!"
Hugh stars alongside James McAvoy, Nicholas Hoult, Michael Fassbender and Jennifer Lawrence in the superhero sequel.