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The teacher - De Niro studied with Hollywood legend Stella Adler, who taught him the all-important Stanislavski system.

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The method - The Stanislavski system (pioneered by Konstantin Stanislavski) is what's known as the "art of experiencing," and is basically an academic term for method acting.

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The lesson - Exploring both the internal and external aspects of a role, De Niro could become the character on-set and off-set, which has led to some incredible stories and performances.

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'Mean Streets' - Robert De Niro and Richard Romanus clashed during the filming of 'Mean Streets.' This added to their on-screen rivalry, and leads up to an important climactic scene, which won't be spoiled here.

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'The Godfather Part II' - De Niro's turn in 'The Godfather Part II' is one for the history books. Playing a young Vito Corleone, the actor spent three months in Sicily to prepare for the role.

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'The Godfather Part II' -

The actor has Italian roots, but he spent around four months learning the Sicilian dialect. Nearly every line he speaks is Sicilian. Of course, the hard work paid off.

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'Taxi Driver' - 'Taxi Driver' helped solidify De Niro as a near-perfect on-screen presence. He famously spent around 15 hours every day driving cars and preparing for the role.

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'Taxi Driver' - He also studied the effects of mental illness, and visited an American Army base in Northern Italy, where he taped conversations with Midwestern soldiers.

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'Taxi Driver' - Co-star Jodie Foster once claimed that De Niro would repeatedly ring her and ask for a coffee date. They reportedly rehearsed their dinner scene over and over, with De Niro refusing to give up.

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'The Last Tycoon' - De Niro was a shining star in Elia Kazan's final film, 'The Last Tycoon.' The actor apparently cut his weight down from 170 pounds (77 kg) to 128 pounds (58 kg) to play the role of Monroe Stahr.

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'The Last Tycoon' - Elia Kazan wasn't quiet when singing De Niro's praises. "[He] is one of a select number of actors I've directed who work hard at their trade, and the only one who asked to rehearse on Sundays. Most of the others play tennis."

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'New York, New York' - In 1977, the actor learned to play the saxophone to portray a sax player in 'New York, New York.' We expect nothing less.

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'The Deer Hunter' - Tensions were high on the set of 'The Deer Hunter,' and the tables were turned on De Niro. During filming, Christopher Walken was persuaded to spit on De Niro, who apparently nearly walked off set in rage.

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'The Deer Hunter' - The characters play Russian Roulette in one scene, taking turns slapping each other. The slaps were real, as was the palpable anger on the actor's faces.

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'The Deer Hunter' - In another scene, Robert De Niro requested a real gun to play Russian Roulette. This helped build more tension, but the chamber was checked in between every take.

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'Raging Bull' - In 1980, De Niro had one of his biggest performances in 'Raging Bull.' He reportedly put on 60 lb (27 kg) and learned how to box for the role.

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'Raging Bull' - De Niro was playing Jake Lamotta, and actually trained with the famous boxer, who apparently said De Niro had what it took to be a real contender.

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'Raging Bull' - The actor went through extensive training, and even entered three Brooklyn boxing matches. With two wins, he hasn't got a bad record.

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'Raging Bull' - To build a brotherhood, De Niro and Joe Pesci lived and trained with each other. Since then, the two have remained friends and frequent collaborators.

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'The King of Comedy' - De Niro was on fire in 'The King of Comedy.' In one scene, he used anti-Semitic slurs against co-star Lewis, to provoke him into a memorable performance.

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'The King of Comedy' - It paid off. Lewis apparently had little experience with method actors, and said "I forgot the cameras were there... I was going for Bobby's throat."

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'The Untouchables' - De Niro didn't have long before they started filming 'The Untouchables.' Although he gained weight to play Al Capone, he also wore pads and pillows to bulk up.

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'The Untouchables' - The actor tracked down Capone's tailors, and asked for identical clothing for his wardrobe. He even insisted on having the same silk underwear, despite the fact you can't see them in the film.

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'Falling In Love' - In the mid-'80s, De Niro reportedly grew weary of being typecast as a mobster. He starred in different films like surreal 'Brazil' and rom-com 'Falling In Love.'

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'Falling In Love' - In the latter, the actor went to great lengths for authenticity. He even had business cards made for his character.

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'Cape Fear' - He was back to method acting in '90s thriller 'Cape Fear.' He worked out for several months and during filming, and reportedly lowered his body fat to just 3%.

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'Cape Fear' - Robert De Niro apparently paid a dentist a large sum to make his teeth look bad. After filming wrapped up, De Niro paid him yet again to fix them.

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'Cape Fear' - His character, Cady, has one creepy southern accent. De Niro apparently taped locals from southern states reading out the script, and mimicked it. It's said that he even rang up Scorsese and left voicemails in the creepy voice.

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'Heat' - For 'Heat,' De Niro deliberately didn't rehearse a scene with Al Pacino, playing up the unfamiliarity between the two characters.

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'The Good Shepherd' -

De Niro's endless commitment followed through into his directing. He couldn't play a part in 'The Departed' due to directing 'The Good Shepherd.' "I wish I could've been able to," he said.

De Niro also features in this list of great actor-director duos.

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