EXCLUSIVE: John Lithgow Spills on the 'Challenges' of Transforming into Winston Churchill on Netflix's 'The Cr

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John Lithgow
is stepping up -- and shrinking down! -- to play Winston Churchill in Netflix's new series The Crown.

The drama, which is rumored to be costing $100 million, will trace the life of Queen Elizabeth II from her wedding in 1947 to the present day. Lithgow was cast to bring iconic British prime minister to life, and the 71-year-old actor is dishing to ET about the behind-the-scenes secrets of his Churchill transformation.

Lithgow credits The Crown's "enormously helpful" makeup department as the true heroes for helping him nail his interpretation of Churchill.

WATCH: 'The Crown,' Netflix's Ambitious New Original Series About Queen Elizabeth II

"All it really was was a wig and two plumpers which clicked onto my back teeth to give me those Churchill jowls. It also helped me with that peculiar voice of his," Lithgow said to ET at a Netflix press event in New York on Wednesday.

"I also stuffed cotton up my nose," the Interstellar star added. All of these little behind-the-scenes details allowed Lithgow to nail Churchill's "remarkable speech impediments and nasal passages."

"I was amazed this morning because Claire For, who plays Elizabeth and who I worked with for 18 months, said, 'John you didn’t have a wig did you?' That's how good the makeup was!"

But there was one physical hiccup that makeup could not change: the considerable height difference between the two men. Lithgow towers at 6' 4", nearly a full foot taller than Churchill's 5' 6" stature.

EXCLUSIVE: John Lithgow Talks Netflix's Queen Elizabeth II Series 'The Crown'

"That was really my biggest challenge and the thing that intimidated me the most," Lithgow confessed of his vertical setback. "I brought it up to our director Stephen Daldry, who we had been rehearsing with for two weeks and I said, Stephen you haven't even mentioned my height what are we going to do about that?"

In the end, The Crown's costuming department devised a padded body suit that Lithgow wore underneath all of his clothes, in order to create Churchill's hunched-over shape and fuller figure.

For a deeper peek at Lithgow's transformation, press play on our video above and don’t miss season one of The Crown when it hits Netflix on Friday, Nov. 4.