Rain Man: Dustin Hoffman legit let a beefer rip and Tom Cruise just went with it.

Blade Runner: In her first scene, Daryl Hannah was running in the rain and crashed into a van window, breaking it and her elbow. On film, it added to her character, so it was kept in.

Nightcrawler: The scene where Lou Bloom is screaming at the mirror wasn’t in the script. Gyllenhall was just trying some things out, and he attacked the mirror, breaking it and cutting his hand. It was so intense, it was added into the film.

Lucky Number Slevin: In the scene where Lucy Liu enters the room to see Slevin naked, he was always supposed to be wearing a towel, but the take they used was an accidental removal of the towel. So her surprise and confusion are genuine.

The Lord of the Rings: The Two Towers: In the scene where Eowyn is staring off into the distance, and a flag is ripped off the pole, that wasn’t supposed to happen. The flag coming off was a complete fluke that fit the tone of the movie.

The Godfather: Most people know the one about the cat in Don Corleone’s lap being a stray, but what about the story of Luca Brasi. He was played by Lenny Montana, who was so nervous acting with Marlon Brando, that he kept on messing up his lines. So they made it a part of his character.

Being John Malkovich: During the scene where a car drives past and someone tells him to think fast, before chucking a beer can at his head, that wasn’t planned. Or at least, John Malkovich wasn’t consulted first. It was a bunch drunk extras goofing off, and it worked in the context of the film.

Apocalypse Now: During the opening scene where Captain Willard is freaking out, Martin Sheen was insanely fucked up. Him punching a mirror, crying, and bleeding everywhere was all for real, and it started off the film on a serious note.

Casino Royale: The iconic shot of Daniel Craig rising out of the water, much like Ursula Andress in Dr. No, wasn’t actually scripted. He was just supposed to float away, but Craig hit a sandbar and decided to get up and walk to another part of the beach.

The Princess Diaries: When Anne Hathaway is walking up the bleachers, and falls between the seats, that was all genuine. The director thought it was so authentic to the character, that he kept it in.

Eternal Sunshine of the Spotless Mind: In the scene when Kate Winslet’s character disappears, Jim Carey didn’t know that she wasn’t in the scene, and had a genuinely panicked reaction. That truthful reaction really worked out for the film.

The Usual Suspects: If some one was a Type-A director and they insisted on shooting a scene as scripted, this one would have given them a fit. But not Brian Singer. Between a case of the giggles and a nasty Benicio Del Toro fart, this is one of the best scenes in the film.

The Silence of the Lambs: In the scene where Hannibal Lector is detailing his crimes and he hisses at Jodie Foster, her jump is genuine. Makes him that much more of a creepy villain.

Scent of a Woman: Al Pacino loves to go method when he’s getting into a part, so for this one, he got used to letting his eyes stay unfocused. He got so good at simulating blindness, he could barely see anything. So, the scene where he falls over a garbage can was a complete accident, but worked well in the context of the film.

Thor: When Anthony Hopkins has to banish Thor from the realm and takes his hammer, he also throws an unscripted snarl at Loki. This was from Sir Anthony being so in character and just so angry that he lost control. The shock on Tom Hiddleston’s face was real.

A Few Good Men: During the most intense scene, Jack Nicholson was supposed to say “You already have the truth.” But when it came time to deliver it, he messed up his lines, and delivered something even more iconic. It was a no-brainer to keep in.

Midnight Cowboy: When a rogue taxi got too close to Dustin Hoffman, he yelled out “Hey, I’m walking here!” And one of the most quoted lines in cinema history was born.

Zoolander: When talking to the hand model played by David Duchovny, Stiller repeats the line “But why male models?” because he kept on forgetting his next line. And Duchovny’s deadpan response was very genuine. It just works.