George Clooney loves tormenting the extras on his movies.

The 46-year-old star has revealed he made the minor actors on his 2005 film 'Good Night, and Good Luck' roll in mud for a scene he never intended to use.

George recalled: "I kept them on for an extra three or four days and told them we had to do reshoots in the mud. I kept them on pay for almost a week."

"We kept bringing them out to the set and then sending them home. Then finally, on the last day, we had them rolling around in a big tub of mud. We stood them with the green screen and shot them but we told them we didn't really need the shot. That was funny."

George - who both directs and stars in new American football movie 'Leatherheads' - believes you have to be vain to combine the roles of actor and filmmaker.

He said: "It's hard because it requires such an amount of narcissism that it's embarrassing."

"There's times when it's embarrassing when there are 1500 extras in the stands and you've got a megaphone and you're in uniform and you're covered in mud and you're directing the extras. You feel like a bit of a schmuck, but it's pretty funny."

'Leatherheads', which also features George's close friend Renee Zellweger, hits cinemas later this month.