Ryan Gosling and Michelle Williams lived together for a month, with their on-screen daughter, so they could mirror the rhymths of a family in Blue Valentine.
Tom Hanks lost so much weight for his roles in Philadelphia and Castaway that he credits the yo-yo dieting for his eventual type II diabetes diagnosis.
Christian Bale is a notorious Method actor who relishes gaining and losing weight for his roles, but nowhere was his dedication more apparent than in his chilling transformation for The Machinist.
To play an AIDS victim in Dallas Buyers Club, Matthew McConaughey ate egg whites and chicken and lost over forty pounds.
Renee Zellweger ate 4,000 calories a day to gain twenty pounds to play Bridget Jones—twice. (Okay, it sounds fun!)
Rooney Mara truly pierced her nipple to get into character for her role in The Girl with the Dragon Tattoo.
Heath Ledger was so dedicated to his role as the Joker in The Dark Knight that he locked himself in a London hotel room for a month to experiment with voices and get into the character.
Jared Leto stayed in character as transgender Rayon for his critically acclaimed role in Dallas Buyers Club, and lost a whole bunch of weight in the process, too.
Joaquin Phoenix announced a retirement from acting, and a foray into rapping, and generally acted like a total weirdo for months before claiming he was in character for a mockumentary, I'm Still Here.
Director Roman Polanski reportedly made Adrien Brody practice piano up to four hours a day for his role in The Pianist, though it paid off with an Oscar.
Shia LaBeouf clearly loves suffering for his art, but one imagines he didn't suffer a whole lot when he actually had sexual intercourse on film in Nymphomaniac.
Natalie Portman shaved her head for V for Vendetta, then trained in ballet for 8 hours a day and lost tons of weight for her Oscar-winning role in Black Swan. Get it, girl.
Daniel Day-Lewis is one of the most dedicated Method actors in Hollywood, notably signing his text messages "A" while playing Abraham Lincoln in Lincoln. But he also worked at a cerebral palsy clinic for two months and was pushed in a wheelchair for his role in My Left Foot.
Nicolas Cage pulled out two of his teeth to play a Vietnam vet in Birdy. They were baby teeth, he claimed, but still!
Anne Hathaway survived on two oatmal paste squares every day to drop weight for her Oscar-winning role in Les Miserables, as well as chopped off her hair.
Forest Whitaker learned Swahili so he could ad lib dialogue for his role in The Last King of Scotland.