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Actors must be able to transform themselves into various different characters throughout their career. Sometimes this calls for extreme measures to prepare their mind and body for the role. In the following gallery, browse through some of the most extreme things actors have done while preparing for a role.

▲Deceased Australian actor Heath Ledger went all out in preparation for his role as the Joker.

▲He locked himself in a hotel room for six weeks while depriving himself of sleep and downing prescription medication in order to fully immerse himself in the psyche of the maniacal Joker.

▲The entire cast of the movie went through vigorous boot camp training to prepare for their roles as soldiers.

▲American actor Matt Damon was the only one who did not have to attend the rigorous physical training sessions. Director Steven Spielberg wanted the rest of the cast to resent him in the hope that it would carry over into their acting.

▲American actor Mickey Rourke put his all into embodying the Russian character Ivan Vanko.

▲He learned his lines in Russian, bought accessories with his own money, and even visited a Moscow prison.

▲For the 1975 film that takes place in a psychiatric facility, all cast members spent time living in the Oregon State Hospital in the United States.

▲The cast interacted with actual patients, who later would take part in the movie as extras. Most of the actors were also relatively unknown at the time, which made it difficult to tell which patients were real and which were actors, in turn making the movie seem all the more realistic.

▲American actor Adrien Brody played the role of a Holocaust survivor in 'The Pianist.'

▲In order to try to understand the depth of loss that was experienced by his character, he broke up with his girlfriend, and gave up all of his belongings and Hollywood lifestyle.

▲American actor Jared Leto is said to have done some pretty crazy things while filming 'Suicide Squad', according to MTV.

▲Playing the diabolical Joker, he sent fellow cast members creepy presents related to their roles, including a dead pig, and never once broke character while on set.

▲English actress Kate Winslet played an older woman who had an affair with a teenage boy during World War II in 'The Reader.'

▲As she needed to speak with a German accent to play the part, she reportedly read to her children excessively while practicing the accent, according to Diply.

▲American actress Rooney Mara went through some physical modifications to play investigator Lisbeth Salander in the 2011 film.

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In addition to cutting and dyeing her hair, she loaded herself up with piercings, including in her ears, nose, eyebrows and lips.

▲In 'The Fugitive,' American actor Harrison Ford plays Richard Kimble, a man escaping from the law after being wrongfully accused of killing his wife.

▲As his character was a surgeon, it was rumored that Ford spent time observing real-life heart surgeries in preparation for the role, according to Screen Rant. He also tore a ligament while on set and instead of getting medical attention, used the limp in his performance.

▲American actress Michelle Williams starred in this film about one of the most popular celebrities of the 1950s.

▲The actress studied hard for the part, doing extensive research on Monroe's mannerisms and personality by watching hours of interview footage. She also tied a belt around her knees in order to simulate Monroe's walk.

▲Famous American actor Tom Cruise played a stealthy assassin in the 2004 crime-drama 'Collateral.'

▲Cruise dedicated himself to learning how to blend into crowds in preparation for the role, in addition to shooting guns with live ammunition. He even dressed up in a FedEx employee uniform and delivered packages, all while attempting to go unnoticed.

▲Israeli-American actress Natalie Portman won an Academy Award for Best Actress for her role as ballerina Nina in 'Black Swan.'

▲In order to perform the gorgeous dance pieces in the movie, she underwent a year of daily eight-hour training and lost 20 pounds.

▲Canadian actor Ryan Gosling and American actress Michelle Williams star as a married couple in this romantic drama.

▲They lived together with their on-screen daughter for an entire month before beginning filming as a way to integrate as a family and get used to playing the parts.

▲American actress Anne Hathaway is another who went through extreme physical transformations to play the role of a starving prostitute in this musical-drama.

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She lost 25 pounds by eating an extremely restrictive diet, and cut off almost all of her hair.