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From Normal Teen To 'Game Of Thrones': Young Cersei Tells Us What It's Like

Nell Williams takes us behind the scenes of the "Game of Thrones" process.

If you landed a plum role on an episode of "Game of Thrones," your first move would be to rub it in the jealous faces of your bosses/teachers/colleagues/classmates and so on and so forth, right? Then continue to torture them with this information until the end of days?

Well, for 16-year-old Nell Williams, who guest starred as Young Cersei on Sunday's (April 12) premiere, the answer to that question is a definitive "no." In fact, as of press time, Williams' classmates still had no clue they'd be seeing her on the "GoT" premiere, which airs Monday nights in the U.K.

"I told a few of my friends who have been sworn to secrecy," she told MTV News ahead of the episode's airing. "I think people at school are going to get a bit of a shock tonight. It’s really, really hush-hush... I had to sign a contract that signed away my rights to the universe about putting any pictures on social media of any costumes, or hair, or literally anything. I couldn’t put it anywhere until tonight."

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The entire process for Williams began months ago, when she went into her audition knowing she'd be trying for Young Cersei -- only she'd never seen the show, or read any of George R. R. Martin's books. In the few weeks between landing the part and flying off to Ireland to film it she tried to read "A Song of Ice and Fire," but to no avail. Instead, she studied four years' worth of Lena Headey playing Cersei, and admitted that learning what makes that character tick was the hardest part.

"I got the accent quite quickly, but what was quite difficult was finding out what made her her," Williams explained. "She’s obviously very nasty; extremely nasty. Because I was playing her when she was younger -- she couldn’t always be horrible. She could be a bit stuck up when she’s younger, but I think the importance of this scene is making sure the audience knows how she became the person she is. And that was really interesting to do. So I just had to find out as much as I possibly could about her."

When Williams finally arrived on set last summer, weeks before the rest of the cast (minus Kerry Ingram, who plays Shireen Baratheon) had arrived, she said the craziest part was getting used to all of the behind-the-scenes props that makes "Thrones" feel so realistic.

"You step off the plane and arrive at the unit, and it’s all these massive, enormous warehouses," she said. "You go inside, and they’re filled to the brim with props of like, dead people’s heads. It's all weird things in these warehouses. There were horses in one... It was very, very easy to slip into the imaginary world that you have to put yourself in, just because the props and everything are so realistic. It’s really weird."

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Weirder still is how it took two weeks of on-and-off filming to nail Williams' five minute-ish scene, which would have wrapped in a matter of hours on a show with a lesser budget.

"They film about, I don’t know, a minute a day?" Williams explained. "When we filmed a whole day, it accounted to about a minute, I would say... it’s a really, really step-by-step process. That was obviously helped by the crew and everyone. They were amazing. Everyone knew what they had to do, how long they had to do it, when they had to get it done by, what it had to look like in the end. It was really, really amazing."

Less amazing, however, was the availability of bathroom breaks when you're dressed like Cersei Lannister.

"[The dress] was so heavy, and it was boiling as well in the studio," Williams said. "There were all these massive lights on because they had to get the lighting right, and there was also a fire in the hut. With all of that and like 30 people in one room trying to film, it got really hot so quickly, and the costumes were down to the floor with loads of layers. So it was boiling, and also really difficult to go to the loo because you have all these massive skirts and everything. But it was definitely worth it."

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