Martin Scorsese told Stephen Colbert that one of Robert De Niro's most famous lines of all time wasn't even scripted.

Director Scorsese gave shocking news thursday episode “Late Show”. Most fans will remember the most famous line from the iconic film Taxi Driver, when De Niro, who plays night shift taxi driver Travis Bickle, looks in the mirror and says, are you talking to me? Well, I'm the only one here. ” Scorsese said that De Niro was responsible for all of the famous lines.

Colbert was shocked to learn that the most memorable line in the film was improvised.

“He was improvising,” Scorsese explained. “We were behind schedule. We were in a lot of trouble.”

The Academy Award-winning director told Colbert that he was behind schedule and under pressure to cut scenes, but he continued filming knowing De Niro was up to something.

“They were banging on the door, so I had to go to the door, open the door, and say, 'This is good.'” This is good. Give me five minutes, two more minutes,” Scorsese said. “And I said, 'Do it again, do it again!'” And he was doing it with movement and a gun. ”

“So if I had followed the plan, I wouldn't have been like, 'Are you talking to me?'” Colbert asked incredulously.

“That's right. That wasn't in the script, it was a word from him,” Scorsese responded. (Related article: Jennifer Lawrence explains the strange reason she asked Robert De Niro to quit their wedding rehearsal)

Taxi Driver is consistently ranked by fans and critics as one of the greatest films of all time, and De Niro's famous line is one of the most iconic in film history.