"It's crazy, but what can you do?," says De Niro, who first uttered the line as crazed Travis Bickle in 1976's Taxi Driver. "It must have struck something with people. I think a lot of people probably do that. It's something that anybody can relate to."
De Niro himself actually gets a chance to poke a little fun at the famous line in his latest pic, The Adventures of Rocky & Bullwinkle. He utters the line as Fearless Leader and winds up getting one of the biggest laughs in the movie.
"When [director] Des McAnuff asked me if I wanted to do that, I said, 'All right, let me try, what the hell,' " he tells TV Guide Online. "So I started studying the scene to see how I had actually said it. I did it verbatim, you know."
While De Niro's best known for his dramatic roles, the actor says it was "fun" getting to play in a movie based on a cartoon. "There's not the pressure of worrying about whether you're believable or not. There's a certain type of believability, but not the type that I'm used to using or working for."
But not everybody's happy about DeNiro's latest role. "One of my kids, my 4-and-a-half-year-old son, didn't like that I was playing the bad guy," he says. Catch De Niro this fall in another comedy, Meet the Parents, co-starring Ben Stiller and Blythe Danner.