• Nikolaj Coster-Waldau films a scene with Lena Headey who plays his twin sister Cersei Lannister.

Nikolaj Coster-Waldau films a scene with Lena Headey who plays his twin sister Cersei Lannister. (Photo : YouTube / Godo :D)

The "kingslayer" Jaime Lannister actor of "Game of Thrones," Nikolaj Coster-Waldau is among the cast and crew who are pranksters on the set of HBO's hit series. The other pranksters are showrunners Dan Weiss and David Benioff. The drama is full of shocking twists and turns that even its cast could not identify which rumors are for real so they can easily be pranked.

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Benioff and Weiss are not making it easier for the cast and they played pranks with them backstage using fake scripts as well as dodgy haircuts and costumes as topics. Kit Harington and Alfie Allen have become targets.

A phony script which said Allen's character Theon Greyjoy died after Bran stabbed him was presented to the actor who did not doubt it at all. The 29-year-old English actor did not complain and went on a holiday, as he told Entertainment Weekly. However, the writers had to make it clear to him it was just a joke.

In season 3, Harington who plays Jon Snow was made to believe that he had to play his character with a permanent grin prosthetic mouthpiece. He got the script which said he was caught up in fire and survived but his lips melted off. So the need for prosthetic and the Jon Snow actor believed it.

Though Harington thought it looked weird, he was fine and determined to make it work, Coster-Waldau told Peter Travers on ABC News' "Popcorn with Peter Travers." The makeup artist told Harington it would be quite big and will take four hours to put on.

"[Harrington said], 'Oh all right, OK. That's great.' But of course he walked on set, and they couldn't -- they started laughing," the Danish actor said.

The showrunners were being pranked themselves by the Jamie Lannister actor. "I had longer hair earlier on in the show, and there was constantly talk about...What's going to happen with the hair?'" Coster-Waldau told Travers.

Coster-Waldau wrote Weiss and Benioff a long letter which read: "Listen guys, I just feel as an artist I'm being left out. And I need my own integrity. I have to take control of my character. Because Jaime is a soldier, I want him to have a buzz cut, so I'm going to go ahead and do that."

The actor added he hoped he would be respected as an artist for doing such. He promised to send a photo when the haircut is done and he did send the next day where he was nearly completely shaven. The photo was from a TV pilot he did in 2009.

Weiss and Benioff were freaking out completely, and had the hairstylist hold the wigs as wigs cannot be made in 24 hours. Coster-Waldau said: "It was amazing. It was a beautiful moment...I got them really bad."

Coster-Waldau was also asked how he managed to make his character noble and likable despite being in an incestuous relationship with his sister. The actor views the relationship sans the morals since the two characters started the affair when they were young and it was what they have known for a long time, he told The Daily Beast.

Watch the video below for some of Coster-Waldau funny moments.