Taxi Driver
Whenever someone talks about the Scorsese classic Taxi Driver, you’ll eventually mimic Robert De Niro and go, “You talkin’ to me?” The famous line was, in fact, not in the script. De Niro was only supposed to look at the mirror, but Scorsese let De Niro assume control over the scene.
The Warriors
David Patrick Kelly’s performance as Luther was easily one of the best things about The Warriors. Now think of the line, “Warriors come out to play!” That line is non-existent in the script and it should be attributed to Kelly! It’s obvious that the director liked it— Kelly even repeated the same line multiple times.