Acting is a weird profession. You’re mostly strangers with someone and then you’re cast in an upcoming project together and suddenly, you’re spending months together practically joined at the hip on set, especially if you have a lot of scenes together. What’s more, film sets aren’t quite the constant action and bustle that you might think – most of what an actor does on set is wait around: wait around for their hair and makeup to be finished, wait around for a scene to be set up, wait around for lighting to be adjusted. The result is that actors often have a lot of downtime. Some fill it with working out, reading or playing video games, or relaxing in their trailers.

Others, however, entertain themselves by playing pranks on their costars.

Here are some of the funniest pranks ever played on set by an actor on their costar.

1. Ben Affleck Redecorated Henry Cavill’s Trailer With Batman

On the set of Batman v Superman: Dawn of Justice, Ben Affleck might have been a newcomer to the DCEU but that doesn’t mean he wasn’t a veteran pranker. In a video he posted to Instagram and Facebook, Affleck revealed he’d cleaned out Cavill’s trailer and redecorated it entirely with Batman toys and memorabilia, including a poster for the movie that he scribbled over by drawing glasses on Superman’s face.

We’d have loved to have seen the confused look on Cavill’s face when he walked into his trailer only to discover it filled with art and toys dedicated to his on-screen rival.

2. Kit Harington Once Pranked Rose Leslie So Bad She Threatened To Leave Him

The cast of Game of Thrones grew incredibly close over the years, and none closer than Kit Harington and Rose Leslie, who met and fell in love on set and eventually got married. However, Kit revealed he played a prank on Rose that got him in the doghouse: He put a model of Jon Snow’s severed head in their fridge. When Rose opened the door, she freaked out and started crying, he guiltily admitted.

“She pretty much told me that if I ever did it again, that would be it,” he said. “And I think that’s marriage included.” Can’t say we blame her.

3. Tom Hanks Set Up A Flash Knitting Mob To Prank Julia Roberts

Actress Julia Roberts has a well-documented love of knitting and costar Tom Hanks took advantage of this on the set of Larry Crowne in 2011. During downtime between takes, Roberts was always knitting. So one day, with the help of a production assistant, Hanks arranged for every single crew member to be knitting before she got there. When she arrived, she walked on set to the sight of 50 people knitting away.

Classic Tom Hanks. It was worth it just to hear Roberts burst out with that iconic Julia Roberts laugh.

4. Alan Rickman Pulled A Classic Fart Prank

The late Alan Rickman might have been one of the most respected actors before his untimely passing in 2016 but he wasn’t above pulling a few juvenile jokes on set. On the set of Harry Potter and the Prisoner of Azkaban, Harry Potter himself was the target of Rickman’s prank. The scene of all the Hogwart’s students sleeping in the great hall had a long setup, with the camera starting out wide to take in the entire hall and then slowly moving and zooming in to focus on Harry’s sleeping face. Unknown to Daniel Radcliffe, however, Rickman had put a fart machine in the young actor’s sleeping bag, aided by costar Michael Gambon and director Alfonso Cuarón. Right at the quietest moment of the scene when everything was silent, a giant fart sound rang out throughout the set and none of the actors could keep a straight face.

It might have ruined the scene, but watching Alan Rickman cracking up at his prank was worth an extra take.

5. Simon Pegg Convinced Benedict Cumberbatch To Put ‘Neutron Cream’ On His Face

Sometimes, a joke spirals a little bit out of control, as Simon Pegg learned on the set of Star Trek Into Darkness. Pegg convinced a few people on the crew that ion radiation had been detected on set and they were to protect themselves by dotting a special, protective “neutron cream” on their faces. He was so convincing that a few makeup artists and part of the crew thought it was for real before it escalated to the other actors. By the time they decided to target Benedict Cumberbatch, the entire crew and other actors were in on it. They even got him to sign an agreement to agree to wear the protective cream on his face. Cumberbatch was so convinced the threat was real that he started getting headaches and forgetting his lines. This finally prompted director J.J. Abrams to end the joke and reveal it had all been a prank.

Luckily, Cumberbatch is an actor known for being self-deprecating. He later admitted to being entirely too gullible but thought at the time he was just adhering to some weird set of American safety protocols.

As it turns out, familiarity with one another breeds intimacy and quite a few pranks have involved actors getting buck nekkid to startle their costars, as you’ll see from the next four entries…

6. Chris Pratt Strips Down On ‘Parks And Rec’

During one episode of Parks and Rec, there was a scene where Leslie Knope, played by Amy Poehler, was supposed to be surprised by accidentally seeing Pratt’s character, Andy Dwyer, naked. Pratt was supposed to be wearing a flesh suit, but it was April Fool’s that day so Pratt took it a step too far and decided to forego the suit and go full Monty for real. Her surprise was genuine and that was the reaction they ended up using in the show.

Unfortunately, Pratt hadn’t actually told anyone on set he’d be doing it and he later got a letter from NBC executives reprimanding him for the prank. Hindsight is always 20/20.

7. Michael Madsen Dropped Trou To Prank Alec Baldwin

While filming 1994’s The Getaway, there was a scene in which lead Alec Baldwin’s character, Doc McCoy, was to be surprised. Unfortunately, Baldwin was having a hard time feigning genuine surprise so costar Michael Madsen decided to help him out. Before the next take, Madsen took off his pants and the unsuspecting Baldwin was so surprised that it got a genuine reaction out of him. As with Poehler’s take, that’s the shot that ended up being filmed and used in the movie.

Though in fairness, Baldwin might have been reacting to Madsen’s truly epic wig.

8. Dominic Monaghan And Billy Boyd Lost All Their Clothes

Fittingly for someone playing a character named Merry, Dominic Monaghan was famous for playing pranks on set of the Lord of the Rings movies. One day the crew arranged a little payback, and unfortunately costar Billy Boyd got roped in. When they arrived on set one day, the two actors were given what they were told would be the new shooting script for the day. In it was a scene in which the Hobbits fell out of a huge tree, snagging their clothes on the branches and losing them on the way down and forcing them to cling to each other naked all night in order to stay warm. The crew shot the entire scene as usual before announcing to the two actors that there was no such scene in the movie and they’d just gotten epically pranked.

Hobbits always were a little too trusting and gullible.

9. A Naked Harrison Ford Hid In Carrie Fisher’s Closet

Harrison Ford, Mark Hamill and the late Carrie Fisher forged a close on-screen chemistry with one another in the original Star Wars trilogy. But in an interview that Fisher did for Channel 4’s “Bring Back Star Wars,” she revealed that Ford, 14 years her senior, pulled a memorable prank on the then 19-year-old Fisher. She had left the room and come back to find him gone. Searching for him, she finally found him in her closet pretending to have hung himself with his tie – completely naked.

As you can see, she laughs about it years later. But it’s definitely the definition of “Too much, man. Too much.”

Even so, that’s still not as bad as the next actor, who had a history of playing ruthless pranks on directors…

10. Paul Newman Accidentally Made Otto Preminger Collapse

Paul Newman was one of the coolest actors ever to grace the screen. And he was a big enough A-lister to get away with things other actors couldn’t, like butting heads with the director. When working with director Otto Preminger on the set of Exodus in 1960, Newman got so irritated at the fussy filmmaker brutally rejecting all of the actors’ script suggestions that he decided to play a prank on him. While shooting a fight scene on a high platform, Newman tossed a dummy dressed exactly like him over the side. Preminger thought it was his star falling to his death and was so scared that he reportedly collapsed and required medical attention.

Whoops.

But that wasn’t even as bad as the storied love-hate relationship between Newman and director George Roy Hill, whose tempestuous dynamic was the stuff of legend. Newman’s penchant for knocking directors down a peg or two really jumped out when Hill was concerned. Just read the next three entries…

11. Paul Newman Sawed George Roy Hill’s Desk in Half

While filming Butch Cassidy and the Sundance Kid, Newman once again got upset about a director not taking his scene suggestions. Hill refused to listen to Newman’s suggestions for a particular scene so Newman had Hill’s desk cut in half, prompting it to collapse when Hill sat down on it.

Honestly, Hill should have known better than to mess with the habitual prankster.

12. Paul Newman Sawed George Roy Hill’s Car In Half

You’d think that after the famous Preminger incident and having his own desk sawed in half, Hill would have learned to listen to the veteran actor. But he did not, and four years after Butch Cassidy, the pair reteamed for The Sting. Once again, the filmmaker refused to take Newman’s scene suggestions, so this time, Newman skipped over the desk entirely and sawed Hill’s actual car in half.

Before you think that was far too much, know that Newman bought Hill a brand-new car when he did it.

13. Paul Newman Staged A Car Crash And Scared The S@#t Out Of George Roy Hill

For a third and final time, Hill got what was coming to him in the form of a wicked prank by Newman. While filming Slap Shot, Newman got annoyed at the director for refusing to buy the crew a round of drinks. To get back at Hill for his penny-pinching, Newman staged a horrible car crash with another dummy dressed like him, scaring the bejesus out of Hill.

Third time’s a charm, as that was the last time Newman ever played an outrageous prank on his longtime collaborator.

But no list of on-set pranks would be complete without at least a few entries dedicated to legendary Hollywood prankster, George Clooney, who surpasses even Newman for the title of Lord of the Pranks. He’s pulled so many pranks on his fellow actors and friends that you could do an entire article on his pranks alone. But here are some of his best.

14. George Clooney Slowly Drives Matt Damon Nuts By Altering His Wardrobe

On the set of Monuments Men, Clooney and Damon had a pact that they’d both get in shape. Clooney hatched a diabolical plan, instructing the costume department to take in the pants of Damon’s costume by a tiny bit every few days. No matter how much Damon worked out, he couldn’t understand why it never seemed to be working and he only seemed to be gaining weight.

It wasn’t until well after they’d finished the movie that Damon read an interview with Clooney and learned what Clooney had done to him.

15. Brad Pitt Pranked George Clooney By Convincing The Cast Not To Speak To Him

For once, Clooney was actually on the receiving end of a prank instead of dishing it out. On the set of Ocean’s Twelve, Pitt sent letters to the entire Italian-speaking crew instructing them that Clooney was very method and so they were to refer to Clooney only as “Mr. Ocean” and to never look him in the eye. Clooney couldn’t figure out why the entire crew was acting so weird around him until Pitt finally broke and told him a week later.

Pitt should have known what was coming…

16. George Clooney Plastered Pitt’s Car With Bumper Stickers

Naturally, Clooney retaliated. Unbeknownst to Pitt, Clooney stuck two bumper stickers on his car. One read “I’m gay and I vote” and the other read “Small Penis on Board.” For weeks, Pitt drove around and couldn’t figure out why everyone would honk and wave when he drove past until he discovered the bumper stickers. But the prank wasn’t over and just when Pitt thought he was safe, Clooney stuck another bumper sticker on his car, this one in the shape of a pot plant and reading “F**k Cops.” Pitt had no idea until he was understandably pulled over by the police.

17. His Habit Of Sending Fake Letters To Various Actors

There was the time that Clooney once sent legendary actress Meryl Streep a package of DVDs of dialect coaching, along with a letter supposedly from his buddy, Brad Pitt, that read that “Brad” heard Meryl was going to be playing Margaret Thatcher and thought she might need some help on her dialect and accent. Or the time he sent a letter to Tina Fey and Amy Poehler, supposedly from Matt Damon, complaining about how hurt he was by one of the jokes they’d made while hosting the Golden Globes. Luckily, the pair quickly figured out it was one of Clooney’s infamous letters on fake stationery from his fellow actors. He’s even sent out letters to his colleagues using a fake letterhead from the Oval Office. The prankster has been sending these letters to unsuspecting actors for years.

18. Or When George Clooney Wet Ryan Gosling’s Pants

But it’s not just Clooney’s longtime collaborators and close friends who are the target of a legendary Clooney prank. Ryan Gosling revealed that when filming Ides of March, Clooney had a habit of deploying more subtle acts of sabotage: He’d walk up to Gosling and engage him in a serious conversation. Then when he walked away, Gosling would look down to realize his pants were soaking wet: Clooney had been hitting him right in the crotch with a squirt bottle the whole time.

Basically what I’m saying is, no one is safe from a Clooney prank. Not even you. Check your mail. You might have a hoax letter sitting in it right now.

“I don’t consider them pranks, I consider them a part of life,” Clooney said at AFI 2018. May we all channel his spirit on this April Fool’s Day.