One thing we love about George Clooney and Matt Damon is their history of playing pranks on each other. During an episode of The Tonight Show With Jay Leno, Damon revealed an elaborate prank Clooney played on him while filming The Monuments Men together. Damon became concerned when his pants became tighter despite working out, but as it turns out, he wasn’t piling on the pounds–Clooney was having his pants taken in.

Matt Damon talked about a few topics with Leno last night, including his first Tonight Show appearance where he promoted Good Will Hunting and his The Monuments Men co-star George Clooney. Not surprisingly, some of his chatter about Clooney had to do with pranks. Clooney is known for playing pranks on his Hollywood cohorts, and he managed to pull off one of his best pranks ever on Damon.

During filming for The Monuments Men, which opens February 7, Damon noticed that his pants were getting snug, which was puzzling since he was working out with Clooney. While working out would give most people a little more breathing room in their pants, Damon’s pants just kept getting tighter, and he had no idea why. “I just thought, ‘This can’t be,'” Damon told Leno.

The truth finally came out, but not until after Damon and Clooney finished filming the movie. “I read finally, which answered a lot for me, that [Clooney] had been taking my pants in by about an eighth or a sixteenth of an inch every couple of days,” Damon said. ”I never said anything to him which, of course, he probably loved even more.”

Interestingly enough, even though Damon was never able to put two and two together, he had suspected Clooney of a similar prank a couple years before.

“A couple of years ago I hadn’t been working out and I’d got kind of fat,” Damon said. “I had to go to a function and when I tried on my suit, it was too tight. My immediate thought was that my buddy George Clooney had hired someone to get into my closet and cut down my clothes. I seriously thought that until my wife said, very gently, said ‘Do you think it might be that you’ve put on some weight?'”

Check out a clip from The Tonight Show where Matt Damon talks about the prank George Clooney played on him below.

Image via YouTube