George Clooney pretended to be Brad Pitt to prank Tom Cruise and Meryl Streep

Speaking to talk show host Jimmy Kimmel - who gave him the stationery - he admitted: "Every actor I know I've sent a letter from Bill Clinton.

"I try to find their worst film and I tell them, 'So I was on the plane and [watching your movie].'"

And George admitted his letters from 'Brad' were particularly "brutal", with one note sent to Tom suggesting they make a sequel to their 1994 movie 'Interview with the Vampire' - but that they swap roles.

George said: "I sent it to Tom Cruise, saying they want to do ['Interview with the Vampire 2'], but this time Brad wants to play Lestat."

Jimmy laughed: "Brad this afternoon said that Tom called him and said, 'Yeah, it's cool, you can play Lestat, that's fine, I'm OK with that,' and he was like, 'What are you talking about?'"

And when it came to Meryl, the former 'E.R.' star sent her a gift that 'Brad' felt would come in useful for her.

He explained: "I sent [a letter] to Meryl Streep with a box of CDs for dialect and I said, 'This guy helped me with my accent in Troy and I think it could really help you.' "

The 'Men Who Stare At Goats' actor is known for his love of pranks and admitted he deliberately "scared the s**t" out of 'Wolfs' director Jon Watts before he pitched the film to Brad.

He said: "I really made him go through the pitch with me, I made him work on it. 'Tell me how you're going to say it, don't do that.'

"I really just scared the absolute s*** out of him before [he called Brad]."

But George claimed most stars are too scared to prank him back.

Asked if celebrities usually figure out that any bizarre letters they receive are from him, he said: "There's usually some guess involved with me. Usually somehow they figure it out.

"I will say this - once you've done a really dastardly, long-running thing, it's like having nuclear weapons.

"Everyone's so terrified that you can - you know this - somebody called Richard Kind and they wanted to do 'Punk'd' or one of those dumba** shows, and they wanted to like punk me and they called all my friends and they were like 'No! He could put a dead body in my apartment.' "