'Matilda the Musical': How Darth Vader inspired Emma Thompson's 'shocking' Trunchbull

For young readers, few characters loom quite as large as the Trunchbull.

In Roald Dahl's 1988 children's novel "Matilda," Trunchbull is the formidable headmistress of Crunchem Hall elementary school, where she swings a "naughty" student by her pigtails and forces another to devour an entire chocolate cake. She's brawny, brutish – and precisely the sort of challenge Emma Thompson was looking for as an actress.

Thompson disappears into the role of the tyrannical Trunchbull in Netflix's "Matilda the Musical" (streaming Christmas Day), a film adaptation of the 2013 Tony-winning Broadway show directed by Matthew Warchus. She recalls her first time seeing herself in full makeup and costume.

"It was quite shocking," Thompson says. "But my main concern was that it would work for Matthew and the team. They had had 12 years of brilliant Trunchbulls (on Broadway and the West End) – the first one of whom I'd seen and admired so much, I'd written him a fan letter: Bertie Carvel. He's very tall and muscular, and I thought: 'Gosh, that's a big ask. How am I going to live up to that?' "

Here's how Thompson and Warchus pulled it off:

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Why Trunchbull is played by a woman and not a man in 'Matilda the Musical'

In Danny DeVito's 1996 movie of "Matilda," Trunchbull was portrayed by actress Pam Ferris. But in the stage musical, the character was primarily played by men dressed as women.

Trunchbull "is a force of malevolence that goes beyond gender, really," Warchus explains. Given that film is a "more realistic medium," it felt like a great opportunity to let a woman play the part again.

Knowing that Thompson was already a fan of the stage show, Warchus reached out to her about the role and got an instant yes.

Playing someone as absurd as Trunchbull, "she very much understood that it was an opportunity to flex her muscles in terms of the scale of the performance," Warchus says. "But also, she understood that you can drill down into the character and build some sort of psychological authenticity for what makes (Trunchbull) who she is."

Thompson pulled inspiration from a "terrifying" headmistress she had as a child. She also read a biography of British poet Edith Sitwell, who was treated cruelly by her parents and forced to wear heavy, metal contraptions to fix her crooked spine and nose.

"I thought, 'That's the sort of thing that could send you right over the edge as a child,' " Thompson says. "So I thought: 'OK, let's say Trunchbull had a really cruel childhood. Then we could imagine her attacking the children – not because of them, but because of what's going on inside (her). She can't bear the vulnerability of children.' "

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Emma Thompson spent three hours in hair and makeup to get into character

Part of Trunchbull's backstory in both Dahl's book and the musical is that she's a former Olympic hammer thrower. As an athlete, she has broad shoulders and a giant torso,  which were achieved in the movie through considerable padding. Thompson also has "such a friendly face," Warchus says, so prosthetics were used to give her a more severe nose and jawline.

At roughly 6-foot-6, Trunchbull towers over our pint-sized heroine Matilda (Alisha Weir). That illusion of "David vs. Goliath" was created using a variety of inventive camera angles, body doubles and practical techniques such as standing on boxes. Thompson also wore boots with extra-thick soles and was sometimes digitally enhanced to appear much bigger on screen.

In total, it took three hours every day for a team of five people to get Thompson into hair, makeup and costume. Because the film was shot in the heat of the summer, the wardrobe team installed a cooling system inside her costume with pipes and tubes that would pump cold air inside.

"It was a really massive challenge to create all the fittings," Thompson says. She wanted Trunchbull's uniform to appear oily and unkempt, "so you knew somehow that her hygiene was horrible." She also opted not to wear brown contact lenses: "I (needed) as much of myself as possible so that it's unrecognizable but also very, very real."

Matthew Warchus wanted Trunchbull to have the Darth Vader effect

All the prep ultimately paid off for Thompson, who surprised Warchus with her alarming appearance on the first day of shooting.

"I got the team to help me put it all together and I said: 'I'll go to the end of the corridor and get him to come up the stairs. Give me a shout and I'll just come toward him, and we'll see what effect it has,' " Thompson says. "It was very satisfying because he quailed, frankly."

Warchus says he remembers the moment "vividly" of Thompson storming toward him.

"I would often find myself saying, 'The thing is, when Trunchbull comes on set, everybody's pulse has to quicken.' The effect is the Darth Vader-type thing, where you feel unsettled whether you're a child or an adult," Warchus says. "That's not at all what you feel when Emma Thompson walks into a room – you feel like you're with an old friend.

"But when she opened the door and I saw her coming down the corridor, it was genuinely scary in the way that made me giggle. I thought: 'This is so great. We've got our Trunchbull.' "

This article originally appeared on USA TODAY: 'Matilda' movie Netflix: Emma Thompson talks Trunchbull transformation