De Niro's brand of method acting includes employing whatever extreme tactic he feels is necessary to elicit the best performance from those with whom he is working. During the filming of The King of Comedy, he directed a slew of anti-Semitic epithets at co-star Jerry Lewis to enhance and authenticate the anger demonstrated by Lewis' character. According to People magazine, the technique was successful, with Lewis recalling: "I forgot the cameras were there... I was going for Bobby's throat."
Boss Paul Vitti:
Hey, I got news for you, you little two-bit prick, son-of-a-bitch, rat-bastard you did nothing for me! Whatever you did the other day didn't take! I'm still fucked up! You did fucking NOTHING for me!
Dr. Ben Sobel:
Hey, what do you expect? I saw you for five minutes! I can't work miracles, Mr. Viti! And let me tell you something, I do not appreciate it when someone sneaks into my hotel room and kidnaps me in the middle of the night. I have a life, Mr. Viti, I have a family, and I have a serious practice, and I don't have time for your BULLSHIT!... That got away from me at the end there.
De Niro had to turn down a role in The Departed (Martin Sheen taking the role instead) due to commitments with preparing The Good Shepherd. He said, "I wanted to. I wish I could've been able to, but I was preparing The Good Shepherd so much that I couldn't take the time to. I was trying to figure a way to do it while I was preparing. It just didn't seem possible."
Praised for his commitment to roles, stemming from his background in method acting, De Niro gained 60lb (27kg) and learned how to box for his role as Jake LaMotta in Raging Bull, ground his teeth for Cape Fear, lived in Sicily for The Godfather Part II, worked as a cab driver for a few weeks for Taxi Driver, and learned to play the saxophone for New York, New York. He again put on weight for his performance as Al Capone in The Untouchables (1987).>