"I am working on a prank that will end his career. 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," Clooney said while speaking at the Adobe Summit in Las Vegas, reports femalefirst.co.uk.
Clooney, who is married to human rights lawyer Amal Clooney, recalled the time he pranked Pitt with a bumper sticker.
He said: "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 (Toyota Prius)...Because there's no way you're not getting arrested with that."
The "Monuments Men" actor also said he sent actress Meryl Streep a DVD made by a dialect coach and signed it from Pitt, while he also arranged for the "Fury" actor to receive pitch letters, which he pretended were from Tom Cruise and other stars.