When actors go to the extra mile, they usually produce really great films. They get into character so much not just for a good performance, but an exceptionally convincing one. They want to believe they are these characters so much that it would seem as if they aren't acting at all! Check out the list below:

Robert De Niro: Before starring in "Taxi Driver," he became an actual New York cabbie for weeks.

Adrien Brody: He literally gave up everything to portray a Holocaust survivor, including selling his car, apartment, disconnecting his phone, and moving to Europe and not eating much for his role in "The Pianist."

Tom Cruise: For "Collateral," Tom learned how to blend in the crowd by dressing up as a FedEx worker and delivering packages inconspicuously.

Daniel Day-Lewis: In "My Left Foot," he played a cerebral palsy sufferer who can only control one-lumb-his left foot. To prepare, he refused to leave his wheelchair, demanded that he be force-fed, and broke his ribs from remaining hunched over for to long a time.

Gene Hackman: In "The French Connection," Hackman spent a month driving around in a patrol car to get a feel for what detectives really go through and even helped to restrain a rowdy guy into the car.

Nicolas Cage: For Ghost Rider, he painted his face constnatly and carried Egyptian relics to tap into the world of actual ancient ghosts. He also refused to speak to his co-stars during filming so they would be afraid of him. For "Leaving Last Vegas," he got drunk and recorded himself so he could see what he would actually look like intoxicated. For "Birdy," he had two teeth removed without anesthesia.

Halle Berry: She got down and dirty for her role as a crack addict in "Jungle Fever," and didn't shower for an entire month.

Joaquin Phoenix: He was so in to his mockumnetary that while filming it, he made everyone believe that he was retired from acting and that he had lost his mind.

Jim Carrey: For "Man on The Moon," he played comedian Andy Kaufman and his repulsive alter-ego Tony Clifton and even refused to break character the entire time. He put cheese in his pocket so that he would smell horrible while acting.

Al Pacino: For "Serpico," he played an undercover cop and was so deep in the role that one night while driving, he actually pulled over a truck and tried to arrest the driver.