There's Method in the Madness

Notable Method Techniques:

Confined himself to a hospital bed for a month to get into his paraplegic character's psyche for The Men

Notable Method Techniques:

Refused to leave his wheelchair and had crew members carry him around the set. He also insisted that all of his meals would be spoon-fed to him for My Left Foot

Trained for 1½ years to be a professional-standard boxer with former heavyweight champion Barry McCuigan for The Boxer

Taught himself how to live as a survivalist and learned how to hunt animals for food, refusing to eat anything he hadn't killed for Last of the Mohicans

Notable Method Techniques:

Holed himself up in hotel rooms for weeks at a time, where he stayed in character and kept a diary as the Joker for The Dark Knight

Notable Method Techniques:

Endured at least 12 piercings (including her nipple) in one day to fully immerse herself in the role for The Girl with the Dragon Tatoo

Notable Method Techniques:

His constant running to portray sleep-deprived character prompted co-star Laurence Olivier to famously ask "Why don't you just try acting?" for Marathon Man

Notable Method Techniques:

Lost 60 pounds to portray a haunted insomniac by consuming just an apple a day and coffee for The Mechanic

Immediately gained over 60 pounds for Batman Begins

Spent hours in the gym each day and refused to talk to anyone on set for American Psycho

Notable Method Techniques:

Gained 60 pounds to play the older Jake LaMotta after having gone through intense physical training in order gain the muscle mass to play the younger LaMotta for Raging Bull

He paid a dentist $5000 to make his teeth look bad, and then paid $20,000 to have them repaired for Cape Fear

He lived in Sicily for three to four months, learning the local language and way of life for The Godfather Part II

Notable Method Techniques:

Starved his way to a gaunt 114 pounds. Also he waxed his body and brows, and went grocery shopping as a woman for Dallas Buyers Club

Stayed in character throughout the shoot, going as far as to send odd gifts to his co-stars including a dead hog and a live rat for Suicide Squad

Notable Method Techniques:

Was so into character that he attempted to arrest a truck driver whilst playing an undercover cop for Serpico

Took cold showers in order to express a demented state for Dog Dag Afternoon

Notable Method Techniques:

Spend hours a day in a wheelchair with his body contorted, something that caused physical pain and sometimes affected his breathing for The Theory of Everything

Notable Method Techniques:

Slashed his own face for Fury because he wasn't satisfied with the make-up, had his tooth pulled out, and didn't bath for the entire shoot for Fury

Notable Method Techniques:

Practiced the piano for four hours a day until he could play Chopin flawlessly. Also got rid of all his possessions (including his girlfriend) for The Pianist

Asked to be left alone on a gurney, restrained in his character's titular straitjacket for long periods of time for The Jacket

Notable Method Techniques:

Burned his own flesh and ate live octopus (repenting afterwards as it was against his religion) for Oldboy

Notable Method Techniques:

Lived life as a man for at least a month, including wrapping her chest in tension bandages and putting socks down the front of her pants much the same way that Brandon Teena did for Boys Don't Cry

Underwent a serious training schedule to prepare for this film. She gained nearly 20 pounds of muscle due to the workouts. She contracted a bacterial infection from a blister she developed on her foot during training that would have landed her in hospital for three weeks. Instead, she took a week off for medicated rest and didn't tell Clint Eastwood or the producers of the film about the injury, because she didn't believe it was in character for Million Dollar Baby