Unless a director’s number one priority is performance, actors are lucky to get a couple rehearsals before going to camera for a role.

Here are 10 Shocking Ways Actors Prepared For Famous Roles

Heath Ledger in The Dark Knight

What some actors may have approached as a classic comic book villain, Heath Ledger saw as an opportunity to create something more. To prepare for his role of the Joker in The Dark Knight, Ledger secluded himself in a hotel room for about six weeks to develop the psychology and mannerisms of the maniacal clown. With a lot of prescription drugs and very little sleep, he invented a deeply disturbing yet mesmerizing character that silenced all the naysayers. It was a process that left a permanent mark on the actor and on film history.

Cast of Saving Private Ryan

All eight actors playing the soldiers chosen to save Private Ryan had to attend an intensive boot camp training that included a military physical regiment and camping in soaking wet conditions. When they all voted to quit, their votes were overruled by Tom Hanks, who played their commanding officer. As Private Ryan, Matt Damon didn’t have to attend boot camp. Spielberg hoped this would make the rest of cast of resent him, and the cameras would catch them hating Private Ryan.

 Mickey Rourke in Iron Man 2

Serious preparation can be a risky business, and that risk doesn’t necessarily pay off every time. Mickey Rourke was very hands on with the development of Iron Man 2’s Ivan Vanko. Adopting a Slovakian accent, he learned most of his lines in Russian, visited a prison in Moscow, and paid for the character’s gold tooth and pet bird out of his own pocket. All interesting choices, but unfortunately Rourke’s eccentric Whiplash didn’t gel with Marvel’s more straightforward tone.

Cast of One Flew Over The Cuckoo’s Nest

The actors became patients and the patients became actors when filming 1975’s One Flew Over The Cuckoo’s Nest. To create a believable film about life in a psychiatric hospital, director Milos Foreman had the cast live in the Oregon State Hospital and interact with actual patients who became extras in the film. Today it’s easy to recognize Danny Devito and Christopher Lloyd, but apart from Jack Nicholson the cast was all unknown at the time, making it even harder to tell the performers from the patients.

Christian Bale in The Machinest

We’ve all heard of actors gaining or dropping a few pounds for a role, but Christian Bale took it to the extreme in 2004 when he dropped 63 pounds to play an insomniac losing his mind in The Machinist. To achieve this stickily figure, Bale had a daily diet of a can of tuna, an apple, and lots of cigarettes to curb his appetite. This is the most weight anyone has ever lost for a role, and if Bale had his way he would have gone even further, but the producers feared for his health. As soon as filming wrapped, Bale was carbo loading and helping his body bounce back for his first outing as Batman the following year.

Daniel Day Lewis in My Left Foot

No list of actors who went to to extremes for their role would be complete without the king of method, Daniel Day Lewis. The film that first gained him this reputation was My Left Foot, where he played a character suffering from cerebral palsy. Lewis reportedly broke two ribs during filming to help maintain his hunched over position. He also refused to leave his wheelchair between takes and required help for every day activities like eating and dressing himself, just like his character would. It clearly worked as the role would win Daniel Day Lewis his first Oscar.

Harrison Ford in The Fugitive

It’s been rumoured that Harrison Ford prepared for his role as surgeon Richard Kimble in The Fugitive by assisting in actual open heart surgery. Whether or not that’s true, Ford could have used surgery himself when he damaged a ligament in his leg while shooting. Instead he opted to postpone treatment and incorporate the limp into his performance.

Halle Berry in Jungle Fever

Halle Berry’s first film role was not an easy one. Audiences were introduced to Berry as a crack addict opposite Samuel L. Jackson in Spike Lee’s Jungle Fever. Lee originally thought Berry was too attractive for people believe her in the role, so to demonstrate her dedication, she didn’t shower or bathe for the duration of her 10 days on set. Feeling dirty and uncomfortable helped Berry get into character, but she had to apologize to anyone who caught a whiff on those final days of shooting.

Robert De Niro in Taxi Driver

After being cast in Martin Scorsese’s Taxi Driver, Robert De Niro got a cab license and spent a month working 15 hour days as a cabbie in New York City. Even though he’d recently won an Oscar for his work in The Godfather II, he was only recognized once. He also studied mental illness and PTSD suffered by many Vietnam veterans at the time, helping Travis Bickle emerge as a fully formed character who would become one of cinema’s most iconic.

Jared Leto in Suicide Squad

With Heather Ledger’s posthumous Oscar winning performance still fresh in everyone’s memory, Jared Leto had to work extra hard to create his own version of the Joker and separate it from Ledger and Nicholson’s beloved interpretations. On top of working on his lean and mean physique, Leto was heavily involved in choosing the look of the Joker and creeped other actors out on set by never breaking character and sending strange gifts inspired by their roles. The jury is still out the results of Leto’s process, but what we’ve seen so far has made for a pretty sinister Clown Prince of Crime.