1. Heath Ledger in 'The Dark Knight'
When Heath Ledger accepted the role as the Joker, he had plans to make the character his own. And while his portrayal was brilliant, unexpected and unlike anything we'd seen before, the actor told Empire Online that it took isolation for him to be able to get there.
"I sat around in a hotel room in London for about a month and I just locked myself away and formed a little diary and experimented with voices. I ended up landing more within the realm of like a psychopath, someone with no empathy," he said. "It's always a very personal process in terms of how you land in the character's shoes, so to speak. It's a combination of reading all the comic books I could and the script and then just really closing my eyes and meditating on it.
2. Christian Bale in 'The Machinist'
In order to play Trevor Reznik— a mysteriously troubled individual who suffered from insomnia so severe that it affected his physical health— Bale was forced to lose 28 kilograms.
And while most stars who play underweight movie characters have struggled with the repercussions of losing weight in such a short period, Bale told The Guardian earlier this year that it was an "amazing" experience.
"When you’re so skinny that you can hardly walk up a flight of stairs … you’re, like, this being of pure thought. It’s like you’ve abandoned your body," he said. "That’s the most Zen-like state I’ve ever been in my life. Two hours sleep, reading a book for 10 hours straight without stopping … unbelievable. You couldn’t rile me up. No rollercoaster of emotions.” Alas, it doesn’t last. “As soon as you start putting the food back in your stomach, the rollercoaster comes back.”
3. Ryan Gosling and Michelle Williams in 'Blue Valentine'
Gosling, Williams and their on-screen daughter lived together as a real family in their characters' house in an attempt to create real memories so when the time came to film the final portion of the movie, they had actual recollections to draw on.
"We celebrated fake Christmas and put up Christmas trees, and baked birthday cakes and bought birthday presents, and went to Sears," Gosling said. "We fought all day, and then we'd have to take [our characters' daughter] Faith to the family fun park ... whatever we could do to create real memories."
All of the intense emotions their characters experienced in the film were also felt by those who played them. So much so that Gosling admitted he often lost sight of the fact that he was filming a movie.
"Most movies, you have to try and forget you're making a movie, because there are trailers and booms and lights and marks, and it's everywhere," he said. "And with this, you're trying to remember that it is a movie, because it's so easy to get lost in it."
4. Shia LaBeouf in 'Fury'
Unhappy and worried that the fake slash marks on his face which were created by makeup looked unrealistic, LaBeouf decided to take matters into his own hands.
“We were in make-up and they were putting cuts on Shia and I said, ‘Yeah, yeah, it looks good,’” his co-star Logan Lerman told British GQ," And Shia was like, ‘No it doesn’t look real.’ Then he walks out into the hallway and says, ‘Hey man, wanna see something fun? Check this out…’ and he takes out a knife and cuts his face. And for the whole movie he kept opening these cuts on his face. That’s all real.”
LaBeouf also removed his own tooth in a bid to make his character more realistic. Along the way, the actor deservingly won the admiration of five-time Oscar nominee Brad Pitt.
“Oh, I love this boy," Pitt said. “He’s one of the best actors I’ve ever seen. He’s full-on commitment, man. He’s living it like no one else, let me tell you.”
5. Natalie Portman in 'Black Swan'
Aside from having to shed 10 kilograms for the role and spend countless hours in pointe shows which Portman described as "torture devices", the actress also had to contend with a dislocated rib while filming. Moments into a lift, Portman knew she had injured herself but the director Darren Aronofsky reportedly kept her from breaking character.
"Darren was like, 'Film it! Film it! Stay in character, talk in your character's voice!'" she said.
There was no medic on the set of the low budget 2010 film which meant Portman's injury remained unattended to.
6. Leonardo DiCaprio in 'The Revenant'
Despite winning an Oscar for his brilliant portrayal of a frontiersman in the 1820s, DiCaprio said it was one of the most difficult (and interesting) films he's ever been a part of.
“I can name 30 or 40 sequences that were some of the most difficult things I’ve ever had to do,” DiCaprio told Yahoo Entertainment. “Whether it’s going in and out of frozen rivers, or sleeping in animal carcasses, or what I ate on set, I was enduring freezing cold and possible hypothermia constantly."