Harry Potter and the Chamber of Secrets
Up next, we have another fantasy classic. Think back to the scene when Mr. Weasley raised this great question in Harry Potter and the Chamber of Secrets: “What exactly is the function of a rubber duck?” It was unrehearsed and the line did not exist in the screenplay.
Ghostbusters
Even when they are given a complete script, improv actors probably could not help it. Rick Moranis had a background in this craft and this was how he helped bring Ghostbusters to its level of comedic brilliance. Just take the speech his character delivered at the party. Director Ivan Reitman said, “Rick just made all of it up as he was doing it.”