George Clooney Pranked Matt Damon In A Very 'Mean Girls' Way

01/15/2014 05:50 pm ET | Updated Jan 23, 2014

Looks like George Clooney may have watched "Mean Girls" one too many times.

Matt Damon was a guest on "The Tonight Show with Jay Leno" Tuesday (Jan. 14) and told the host that on the set of his and Clooney's new movie, "The Monuments Men," the perennial prankster played a trick on him that reads like a script full of high school meanies.

Apparently, Clooney had Damon's pants taken in every couple of days by "about an eighth or a sixteenth of an inch" which made superhunk Damon think he was gaining a whole bunch of weight -- after the two men's mutual decision to "get in shape"!

"I was working out, and the pants [were getting tighter] -- I said, 'This just can't be,'" Damon explained. "I never said anything to him, which he probably loved even more."

Oy, George. You rascal.

Watch the full clip above.

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