Butt-flashing Bounty Hunter Gerard Butler

Gerard Butler used to flash his butt on the set of 'The Bounty Hunter'.

The Scottish actor was a big practical joker while shooting the movie - in which he co-stars with Jennifer Aniston - and used to amuse the crew by baring his behind.

In a joint interview with 'Access Hollywood', Jennifer said: "You would moon the crew walking by the wardrobe trailer. That's how close our family got!"

Gerard then admitted: "Well, I like to moon."

During filming, Gerard - who has been romantically linked to his stunning co-star - admits he spent a lot of time in Jennifer's trailer because it was so much fun in there.

He said: "Jen has a great team of people around her and I had more fun hanging out at their trailer than I did in my own."

Jennifer - who has insisted her relationship with the heartthrob is purely platonic - enjoyed every moment of filming because Gerard is so funny.

"It was constant, constant laughter! Other past co-stars get grumpy and go to their trailer."

Jennifer and Gerard, 40, became so close during filming, he even organised her 41st birthday trip to Mexico last month.

She explained: "He said to me, 'You come to Mexico all the time and Mexico is really hurting right now because of the swine flu and the drug trafficking and all of this sort of stuff but it's not all of Mexico.'

"These people survive on us coming down and spending money and coming here to these beautiful places. It sort of made sense to say, 'Hey, let's help out Mexico.' Let's shout out to these kids in Tijuana at El Faro and have a good time. That's sort of our birthday celebration this year."