Extreme Transformations Celebs Have Undergone for a Movie Role

She's one of the world's most stunning women but her character in Monster, well, isn't. So to transform into serial killer Aileen Wuornos, Theron thinned out her hair, gained 30 pounds, shaved and bleached her eyebrows and had a procedure done to her skin to give it a weathered look.

Jaws dropped. It also helps that she can act as Charlize also scored her first Oscar for her portrayal.

And Theron did it again for her upcoming movie, Tully, in which she gained 50 poundsto play a stay-at-home mom struggling after giving birth to her latest kid. Oscar No. 2, maybe?

He was a normal dude until he was cast in The Machinist, for which he lost over 60 pounds to play insomniac Trevor Reznik.

He bulked up soon after to play Batman in The Dark Knight trilogy but by 2012, he went the opposite way and gained around 40 pounds to play Irving Rosenfeld in American Hustle.

Your eyes do not deceive you. That IS Cooper, not a random beefy military man whom the Oscar nominee is following as he prepares for his new movie. Bradley put on 40 pounds of sheer muscle for the role of late Navy SEAL Chris Kyle in American Sniper. It almost makes us forget the American Hustle perm. Almost.

Here's good ol' B-Coop, looking like a normal Hollywood dude prior to making American Sniper. But then — BOOM!

After losing 20 pounds for Nightcrawler, he had to build all kinds of muscle — not to mention, learn how to box — for Southpaw. And the results spoke for themselves.

Why, hello there.

For her role as Bridget Jones — which she tackled in 2001, 2004 and again in 2016 — Zellweger would gain weight every time, then lose it again for other projects.

If only it were that easy for all of us to gain and lose pounds.

Speaking of yo-yoing weight, Hill's weight has fluctuated from full to lean over and over for various roles, whether it was gaining 40 pounds for his role in War Dogs in 2016 ...

... or losing it for his upcoming TV show Maniac.

Already petite, she lost a bunch of weight, shaved her head and eyebrows and gots various piercings to play Lisbeth Salander in The Girl With The Dragon Tattoo.

The difference was staggering.

He was the lovable lunkhead from Parks and Recreation, so needless to say he had to lose a significant amount of weight and gain a whole lot of muscle for his Guardians of the Galaxy role.

And did he ever.

Hathaway was so committed to embodying Fantine in Les Misérables, she dropped 25 pounds and chopped off her long hair.

The idea was to look like she was near death. We think she succeeded.

Basically the opposite of Jason Bourne.

After losing 40 pounds for 1996's Courage Under Fire, Matt found roles where he simply needed to add a little muscle to his frame. But by 2009, he was at it again, this time gaining 30 pounds for The Informant!.

Look how pretty he was in Magic Mike.

Soon after, though, he took on the role of AIDS patient Ron Woodroof in Dallas Buyers Club, for which he lost nearly 40 pounds. Yowza.

Leto always looked lovely ... until he signed on to play John Lennon's assassin, Mark David Chapman, in 2007's Chapter 27, which required him to add 67 pounds to his normally lanky frame.

But just when you thought all he had to do was lose the weight to get back into fighting form, he was cast as a transsexual with AIDS in Dallas Buyers Club. That resulted in even more pounds to be lost and by the time filming began, he weighed a reported 114 pounds. At least like Theron and McConaughey, he has an Oscar to show for it.