Good Will Hunting 

Robin Williams acting in Good Will Hunting was so good that we have to include just one more improvised line. As the movie ends, Will leaves a note for Sean telling him thank you. 

The letter is read by Damon as a voiceover, with him saying that he’s going to try and get back together with his girlfriend. He says, “I gotta go see about a girl,” something Sean said earlier. After reading the letter, Williams says out loud “Son of a b**** stole my line.” A great addition and comedic moment to a heartfelt ending.