So, I’m sitting in the back of a taxi and I got a driver by the name of Travis Bickle.

I tell him, “Pull over and put the flag down.  Pull over.”  Then I say, “Cut,” because I’m making a movie, and Bob is doing Travis and I’m doing a cameo playing the jealous passenger in the backseat.  Now, I had all the lines, all Bob had to do was sit there and not say anything and just stare at me with the back of his head, never turn.  But before the next take, Bob took me over and he said,

“Listen Marty, when you tell me to put that flag down,”

I said, “Yeah,”

“Make me put it down.  Because I’m not going to do it unless you make me put it down.”

And that was the most important lesson in screen acting that I would ever experience, because there’s no line between reality and pretend; there’s only truth, and no one finds that truth better than Robert De Niro.

- Martin Scorsese