The notorious practical joker has been playing tricks on his friends and co-stars, especially Brad and Matt Damon, for years, but George has teased that he is stepping up his pranks against Brad with a long-term idea that could have a lasting effect professionally.

“I am working on a prank that will end his career,” George said at the Adobe Summit digital marketing conference. “If you take the time, if you’re willing to sit on one for a couple of years, and just plant the seed... there’s no rush.”

George has previously sent celebrities letters pretending to be Brad, including Meryl Streep, who he sent a dialect coach DVD, but his Ocean's Eleven co-star also pranks him back. In 2004, when they were filming the sequel Ocean's Twelve in Italy, Brad convinced local shopkeepers George had to be addressed as his character Danny Ocean.

Their prank war doesn't stop there. When Brad brought a new car, George stuck a rude sticker on the bumper of the vehicle which lead to his pal being pulled over by police officers.

“I got a bumper sticker in the shape of a pot plant, that said, ‘F**k cops,’ and I put that on the back of his car,” Clooney said at the event, according to “Because there’s no way you’re not getting arrested with that.”

In 2015, he told U.K. chat show host Graham Norton he was cooking up a big prank that could get him into serious trouble, but hopefully his lawyer wife Amal would be able to help him out.

"I'm doing one now that I can't tell you about, but in a year you're going to hear that I've been arrested," he said. "I'm not kidding, because I think I've crossed the line...I have a wife, she's a barrister, I'll be fine."

It is not known if this is the same as the prank which will end Brad's career.