6. Some of Clooney’s pranks go on for years, literally, one such example involves actor Richard Kind. Clooney saw a horrible painting discarded on the street one day and decided to take it home and sign it. He then spent the next year convincing Kind he’d been taking art classes. On Kind’s 40th birthday Clooney presented him with the painting as a gift, saying it was his first work he’d been really proud of. Kind hung the painting in his home for two years before realising he’d been had.

Watch Clooney and Matt Damon in The Monuments Men trailer

7. During ER’s first season Julianna Margulies made her debut ‘Tonight Show ‘ appearance. She decided to ask co-star Clooney for some advice on what to talk about. Clooney gave her an an anecdote that supposedly happened to his mother, involving a doctor's office and the line "I’m not a gynaecologist, I’m a podiatrist.” Margulies decided to tell the story, but what she didn't know was that Clooney had convinced Kelly Preston years earlier to tell the same story. A few years later when the former co-stars were booked to appear on 'The Tonight Show 'together Clooney had producers cut together footage of Preston and Margulies telling the story. However at the last minute George decided against showing it, fearing it would embarrass Margulies too much.

More: George planning 'dream wedding' for fiancee Amal Alamuddin

8. George really does go to some effort to pull off his pranks. On the set of The Monuments Men, Matt Damon was trying to loose weight, so good friend George decided to have a tailor take in Damon’s trousers an eighth of an inch every few days. A very confused Damon was left unable to figure out why he was still gaining weight.

9. Not all of Clooney’s pranks are successful, however. At this year’s Golden Globes hosts Tina Fey and Amy Poehler joked that Clooney would, "rather float away into space and die than spend one more minute with a woman his own age”, the comediennes also jokingly referred to Matt Damon as a garbage man. Clooney’s plan for revenge was to order stationary custom made for Damon and send the comediennes a letter from Matt saying how upset he was about that joke and that his kid now calls him, '‘the garbage man.” Tina and Amy responded by sending Matt two gigantic fruit baskets. The first one came with a note saying they were both really sorry but thought Matt could take a joke, while the second note read, , “If by chance you didn't send us that letter and it was from George Clooney, please let him know that you’ve got to get up a little earlier in the day to fool a couple of girls like this. We’re grown-ass comedians.” George might have been foiled this time but he has promised that the follow up ‘“will be brutal.”

George ClooneyWho will George's next victim be?

10. Now for Clooney’s favourite prank of them all. Back in the early 90s George temporarily moved in with Richard Kind who owned a cat and kept his litter box was in the bathroom. Each day Clooney would empty the litter box without telling Kind who began to worry that his cat was constipated. Kind even took his cat to the vet, but Clooney kept up the rouse for weeks, until one morning Kind got a very big surprise in the little box. Let’s just say Clooney had used the litter box for his own business that morning.