03/14/2014 10:56 am ET

Julianna Margulies Reveals First George Clooney Prank Back In Their 'ER' Days

George Clooney is known beyond Hollywood for his elaborate pranks, and apparently he's been at it for years.

Thursday night, March 13, Clooney's former "ER" co-star Julianna Margulies told "The Tonight Show" host Jimmy Fallon about the first time she was on the receiving end of an infamous Clooney prank.

As it turns out, back when she was an up-and-coming actress on the successful medical drama show, Margulies was invited as a guest on Jay Leno's "Tonight Show" and was asked to bring a funny story. When she turned to Clooney for help, she got much more than she bargained for.

Watch the hilarious clip above to find out how the story unfolds.

Of course, Clooney and Margulies are still good friends to this day. Last November, "The Good Wife" star told David Letterman that Clooney was "one of the most awesome human beings I've ever met ... He treats everyone with respect, no matter whether you're sweeping the floor or the head of the studio. He's just one of those guys."



Mr. Perfect, George Clooney