Movies are typically meticulously planned out, with every detail carefully crafted and rehearsed. However, some iconic films have memorable scenes or even entire characters that were completely improvised. These improvisations have become legendary moments in film history and helped shape the movies into the cultural touchstones they are today. Here are some of the most iconic movies that were improvised:

"The Godfather"

One of the most famous scenes in "The Godfather" is when Marlon Brando, Vito Corleone's character, stuffs his mouth with cotton balls before delivering his lines. This was an improvisation by Brando, who wanted to make the character more memorable and distinctive.

MARA REINSTEIN/ PARADE | The Godfather is a classic film is a true masterpiece that has earned its place as one of the greatest movies ever made in the history of cinema

"Jaws"

In the classic film "Jaws," one of the most terrifying moments is when Roy Scheider's character Martin Brody sees the shark for the first time and utters the now-famous line, "You're gonna need a bigger boat." This line, which was not in the original script, was an improvisation by Scheider, and director Steven Spielberg kept it in the film's final cut, making it one of the most memorable lines.

"Good Will Hunting"

In the touching scene from "Good Will Hunting," where Robin Williams' character Sean Maguire tells the story of his late wife farting in her sleep, Williams improvised the entire monolog. Director Gus Van Sant loved the improvised scene so much that he kept it in the film's final cut, and it has become one of the movie's most emotional moments.

"The Empire Strikes Back"

In the iconic scene from "The Empire Strikes Back" where Han Solo is about to be frozen in carbonite, Harrison Ford famously ad-libbed the line, "I know." This was a response to Princess Leia's declaration of love for him, which was not in the original script. The line has become one of the most iconic moments in the "Star Wars" franchise and has even been referenced in other movies and TV shows.

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"Taxi Driver"

In the famous scene from "Taxi Driver," where Robert De Niro's character Travis Bickle talks to himself in the mirror, much of the dialogue was improvised by De Niro. Director Martin Scorsese encouraged De Niro to improvise to make the scene feel more natural and authentic, one of the film's most iconic and unsettling moments.

"The Shining"

One of the most iconic moments in "The Shining" is when Jack Nicholson's character Jack Torrance breaks down the bathroom door with an axe and yells, "Here's Johnny!" This line was not in the original script but was an improvisation by Nicholson. The line referenced Johnny Carson's catchphrase on "The Tonight Show" and has become one of the most famous lines in film history.

"Annie Hall"

One of the most iconic scenes in "Annie Hall" is when Woody Allen's character Alvy Singer sneezes into a pile of cocaine. This moment was not in the original script but was an improvisation by Allen and co-star Paul Simon.

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"The Dark Knight"

In the climactic scene of "The Dark Knight," where the Joker is hanging upside down and taunting Batman, much of Heath Ledger's dialogue was improvised. Director Christopher Nolan encouraged Ledger to improvise to make the scene feel more intense and unpredictable. The result is one of the movie's most memorable scenes and helped solidify Ledger's performance as one of the best in the history of comic book movies.