While filming Total Recall, Schwarzenegger noticed the Michael Ironside was constantly on the phone between takes. When he broached the subject with Ironside, he was told the he was phoning his sister and that she was currently suffering from cancer. Arnold immediately brought Michael to his trailer and they had an hour long 3 way conversation with the sister about what exercises to do and what kinds of foods she should be eating and really lifting her spirits. Ironside has never forgotten Schwarzenegger's kindness and neither has his sister.

While filming Harry Potter and the Chamber of Secrets, Bella, the Neapolitan mastiff that played Fang, got very protective of Daniel Radcliffe, and would jump in front of him whenever the animatronic spider for Aragog would come out to defend him, resulting in then having to refilm the scene multiple times.

While looking for a tattered coat for the character playing The Wizard in the Wizard of Oz, a costume assistant bought one from a second hand store. When the actor put the coat on he turned the pocket inside out - written in the pocket was the name L.Frank Baum who is the author of The Wizard of Oz books. Baum's widow later identified the coat as actually having belonged to her husband

In Scrubs the Janitor almost never read his script and just improvised his role. Bill Lawrence actually said that in the scripts, he had "whatever Neil says" on his lines.

During the filming of the Lord of the Rings, Christopher Lee corrected Peter Jackson on the sound of being stabbed in the back. From the DVD commentary: "When I was shooting the stabbing shot with Christopher, as a director would I was explaining to him what he should do"... "And he says, 'Peter, have you ever heard the sound a man makes when he’s stabbed in the back?' And I said, 'Um, no.' And he says 'Well, I have, and I know what to do.' "" He had been involved in some super secret operations for the British during WWII, which is presumably where he knew that from.

In Life of Brian, the line after "yes, we're all individuals", "I'm not!" was ad-libbed, bumping the extra up in pay for now having a distinct speaking role.

In Lord of the Rings: The Two Towers when Aragon, Gimli, and Legolas are approaching the pile of smoldering and dismembered corpses looking for Pipin and Mary, Vigo Mortensen kicks a helmeted Orc head and screams, thinking the hobbits are dead and gone. It's a really good scream and 100% authentic. When Mortensen kicked the head/helmet he broke two of his toes. He used the pain and stayed in character. They kept the scene for the movie.

The actors of Saving Private Ryan were put through basic training before filming, EXCEPT Matt Damon so that the other actors would build some sort of unconscious resentment towards his character

Fight Club was filmed in chronological order, and throughout the filming Edward Norton put himself on a near-starvation diet and avoided the sun, while Brad Pitt spent a lot of time at the gym and in tanning salons. The end result is we see Tyler Durden getting stronger and healthier while the narrator withers away.

When Coppola and Lucas (close friends and filmmaking buddies) were planning Apocalypse Now (which George Lucas was originally supposed to direct) they gave a small role to their carpenter, Harrison Ford, in return for Ford's work on a desk for Coppola's office. Ford also got a role in Lucas' American Graffiti a few years prior this same way. During the casting for Star Wars, Lucas needed someone to read Han Solo's lines while actor's auditioned for Luke. He quickly asked Ford to do it, and afterwards, one of the producers there came up to Lucas and pointed out that he already had his Han Solo in Ford. (Thus beating out Kurt Russell for the role).

One of my favorites is from Predator "Jesse Ventura was delighted to find out from the wardrobe department that his arms were 1" bigger than Arnold Schwarzenegger's. He suggested to Schwarzenegger that they measure arms, with the winner getting a bottle of champagne. Ventura lost because Schwarzenegger had told the wardrobe department to tell Ventura that his arms were bigger."

In The Shawshank Redemption, there's a scene where a guy feeds a maggot to a crow. The American Humane Association made them find a maggot that had died of natural causes to feed to the crow. They wouldn't have given the "no animals were harmed in the making of this film" at the end if they hadn't.

While filming Guardians of the Galaxy, they had to do several takes of some scenes because Chris Pratt kept making the pew pew sounds when he fired his raygun.

Don't know if it's that great, but it's my favourite: In the Dark Knight, whenever The Joker is leaving the hospital as it explodes and then pauses to fiddle with the detonator when the explosions stop, that wasn't supposed to happen and Heath Ledger fiddling with the detonator was ad libbed and Nolan decided to keep rolling and include it in the film

Apparently the scientists for Interstellar did so much theoretical physics to get the wormhole and black hole effects right that their work is going to be published into a scientific paper. Can't find a source on that right now though.

I like the one about Raiders of the Lost Ark where Indy shoots the sword fighter. He was supposed to fight him in a shoot that would've taken 3 days. However Ford was really sick from dysentery and so convinced Spielberg to do it this way.

In Raiders of the Lost Ark, the snakes, being cold-blooded, went towards the thrown torch, causing the director to complain at the snakes, "you're ruining my movie!"

The big reveal that Darth Vader is Luke's father was a crazily guarded secret--even the actor who played Vader didn't know. As most people know, Vader's body was played by David Prowse, and his voice was James Earl Jones. During filming though, Prowse did say his lines. During that scene, what he actually says is "Obi-Wan killed your father." Hamill was only told moments before what the actual line was going to wind up being and none of the other actors knew--no one knew except Lucas, the director, and some producers.

In Goodfellas, the spaghetti they're eating was cooked by Scorsese's mother.

Three people were struck by lightning during the filming of The Passion of The Christ.

In Anchorman, during the Sex Panther scene, Paul Rudd was determined to make Will Ferrell laugh and break character since it was always the other way around. He thought that this would be accomplished with the "60% of the time it works, every time" line. Will fired back with "that doesn't even make sense" line without skipping a beat once again making Paul/Others break character yet again.

In the flower shop scene in "The Room", when Johnny says "oh hi, doggy", that was a genuine reaction. He didn't realize that the dog was - in his own words - "a real thing".

In Hitchcock's Rope, which is composed of just a few very long takes, the dollycam (which is extremely heavy and on rails) ran over a crewmember's foot, breaking it. This was pretty deep into a good take from what I recall, so another stagehand just covered his mouth and dragged him off set rather than let his screams of pain ruin a lot of work.

William Friedkin had a shotgun with blank shells that he'd shoot off on the sound stage during breaks, while filming The Exorcist. It scared the daylights out of everybody, and after a few times he was asked to stop. The actors didn't find it funny. What they didn't know was that their reactions were being filmed - and later inserted into the movie as their reaction when Regan made a sound upstairs.

When Andy Dwyer shows up at Ann's house naked in Parks and Rec, Chris Pratt is actually nude. That is Amy Pohler's actual reaction.

Apparently Ronald Reagan was amused by Doc Brown's disbelief that an actor like him could become president, so much so that he had the projectionist stop and replay the scene. He also seemed to enjoy it so much that he even made a direct reference of the film in his 1986 State of the Union address: "As they said in the film "Back to the Future", 'Where we're going, we don't need roads.'"

In A Knight's Tale, the scene where Mark Addy says "Yayyyy" because the audience gives no reaction to Chaucer was improvised by Addy because the extras didn't speak English (they were Eastern Europeans) and had no idea when to cheer.

I think it was in the Shining, the kid didn't know they were making a horror movie.

(Spoiler alert) In Back to the Future, Marty's family is very wealthy (or at least much wealthier) at the end in the new time. Crispin Glover, who played George McFly, disagreed with the morality of the ending and contested it. Because he was contractually obligated to finish the film, however, he did. He did not, though, appear in either of the sequels. To remedy this, Robert Zemeckis and Bob Gale (co-creators) put in a look-alike wearing huge sunglasses, and used footage from the firsts movie to make it appear as though Glover was in the sequels. Upon seeing this, Glover sued the two, and now there are stricter regulations about this sort of thing.

Anyone who fell asleep on the set of Inglorious Basterds was photographed with a giant dildo next to them.