When actors make a movie, it usually means that they will spend quite a few months, if not longer, together. They will then probably need to travel together to promote the movie, so it helps if they can become friends with each other.

Actors who become tight while filming a movie often liken the experience to a family, a close-knit group. And most of the time, somewhere in these groups - there's a prankster.

Actors have to work hard, so many of them like to break the tension by playing a little practical joke on their co-stars from time to time. Most of their pranks are childish, but that doesn't make them any less funny.

It seems that Hollywood is bursting at the seams with pranksters, so today we're taking a look at who has the best on-set jokes in town. Let's check out the top movie set pranksters and what kind of hijinks they get up to.

15 Tom Hanks Pranked Julia Roberts And Her Love Of Knitting By Getting Everyone To Knit As She Walked In

Larry Crowne
Via imdb.com

Julia Roberts loves to knit so Tom Hanks decided to prank her by getting everyone on the Larry Crowne set knitting. She later explained: "I come onto the set to work one day and every single person on the set everywhere — every grip, every electric, every everything is knitting... You walk into a room and 65 men are knitting."

14 Mel Gibson Pranked Jamie Lee Curtis By Wearing A Hockey Mask

Jamie Lee Curtis
Via ultimatemovierankings.com

While working with Jamie Lee Curtis on Forever Young, Mel Gibson decided to prank her in true horror movie fashion. He snuck up to her door wearing a hockey mask and burst in wielding a knife. Gibson also once sent Julia Roberts a dried out rat as a joke. Wow, okay, then.

13 Penélope Cruz Had To Dress Up As Mr. Hankey From South Park Character After Losing A Bet With Johnny Depp

Pirates-of-the-Caribbean--On-Stranger-Tides

After losing a bet with Pirates Of The Caribbean: On Stranger Tides co-star Johnny Depp, Penelope Cruz had to perform a hilarious forfeit. She had to wear a costume based on the South Park character Mr. Hankey, the Christmas Poo, to the set and pose while Depp took pictures. We'd love to see those!

12 Josh Hutcherson Stank Up Sam Claflin's Trailer With Skunk Spray

sam-claflin-hunger-games
Via flipboard.com

Josh Hutcherson was the biggest prankster on the set of The Hunger Games: Catching Fire. By far his smelliest joke involved a bottle of something that co-star Sam Claflin said reeked of skunk droppings. Josh snuck into Sam's trailer and put some of the liquid on a tissue in the trash. Needless to say, it really made a stink.

11 Christian Bale And Bradley Cooper Pranked Jennifer Lawrence With A Fake Headstone

Christian Bale;Bradley Cooper
Via massive.com

When Bradley Cooper and Christian Bale heard that their American Hustle co-star Jennifer Lawrence was nervous about shooting a scene in a graveyard, they had an idea for a macabre prank. The pair got the props department to make a fake tombstone engraved with Lawrence’s name and birthdate. Jennifer completely freaked out when she saw it, and who wouldn't?

10 George Clooney Arranged For Matt Damon's Clothes To Slowly Get Smaller

monuments men
Via youtube.com

George Clooney is well-known as a Hollywood prankster, so his co-stars are used to his antics. But Matt Damon could never have suspected that Clooney was pranking him during the filming of The Monuments Men. Clooney secretly arranged with the wardrobe department to slowly take in Damon's clothes, because he knew his co-star was trying to shed a few pounds.

9 Alan Rickman Pulled A Classic Fart Prank While Filming Harry Potter

BTS Harry Potter
Via fanpop.com

While filming the scene in Harry Potter and the Prisoner of Azkaban where all the children are sleeping in the Great Hall, Alan Rickman proved that you're never too old for a fart joke. He hid a fart machine inside Daniel Radcliffe's sleeping bag then let it rip right in the middle of a dramatic developing shot.

8 Harrison Ford Hid In Carrie Fisher's Closet

carrie fisher star wars
Via: 20th Century Fox

Years after making Star Wars, Carrie Fisher revealed how Harrison Ford had gone to great lengths to try and scare her on the set. One time he even hid in her closet, barely clothed, and waited for her to open the door. Imagine trying to work with a joker like that!

7 Thandie Newton Put A Mashed-Up Chocolate Bar In Simon Pegg's Trailer Toilet

run-fatboy-run
Via justwatch.com

While making Run Fatboy Run, Thandie Newton pulled a classic childish prank on co-star Simon Pegg. She explained: "I created a human stool out of a king-size Mars bar and placed that in his toilet bowl with a little apple juice around the edge for authenticity... It was a prank and a snack all in one."

Related: 9 Actors Who Were Fired For Surprising Reasons (And 5 Who Deserved It)

6 Brad Pitt Gave Jonah Hill's Golf-Cart A Bright Pink Makeover

moneyball
Via washingtonpost.com

While making Moneyball, Brad Pitt decided to prank Jonah Hill by giving his golf cart a crazy makeover. Pitt gave the cart a pink paint job, rigged it to play Wake Me Up Before You Go-Go by Wham, and wrote "I am Jonah Hill and I love Wham!" on the windscreen.

5 Nick Nolte Pranked Sean Penn By Telling Him He Needed Bail Money

the thin red line
Via imdb.com

While filming The Thin Red Line, Woody Harrelson arranged for Nick Nolte to phone co-star Sean Penn, requesting money to bail him out of jail. When Penn arrived at the police station he found Nolte sitting in a cell, but the next moment Harrelson appeared dressed like a crazed prison guard and raced toward him, waving a gun.

Related: 20 Actors Who Went Too Method For Their Own Good

4 Chris Pratt Hilariously Cropped Jennifer Lawrence From All His Behind The Scenes Photos

Passengers
Via hollywoodreporter.com

While filming Passengers, Chris Pratt played an ongoing prank on his co-star Jennifer Lawrence. He continually cropped her out of behind the scenes and promotional Instagram photos. But Jennifer got her own when she defaced his image on the side of a bus during a Jimmy Kimmel Live appearance.

3 Taron Egerton Put A Mannequin In Channing Tatum's Bed

kingsman
Via businessinsider.com

Taron Egerton decided to prank co-star Channing Tatum by placing a life-sized mannequin in his bed. To make it look more realistic, he added a blonde wig and left a pair of high heels next to the bed. The Kingsman 2: The Golden Circle star was fooled - he thought there was a real stranger in his room.

Related: 20 Movies These Actors Regret Starring In

2 Tom Cruise Pranked Simon Pegg By Turning His Car Seat Heaters All The Way Up

mission impossible
Via flickeringmyth.com

While filming a chase scene for Mission: Impossible – Rogue Nation, Simon Pegg and Tom Cruise spent five days together shooting in a car. On day three, Pegg noticed that he was getting really hot, hotter than anyone else, and he soon worked out that Cruise had been secretly turning his car seat heater on full.

1 Emilia Clarke Put Fish In Sam Claflin's Socks

me before you
Via usatoday.com

There was an ongoing prank war between Emilia Clarke and Sam Claflin on the set of Me Before You. Clarke secretly put fish in her co-star's socks and even placed a fart machine in his (character's) wheelchair. He retaliated by removing all the furniture from her room, only leaving her books behind.

Next: 20 Actors Speak Out About Their Most Difficult Scenes