Directors are in charge on set, but they can't control everything. That's what second takes are for, after all.
But sometimes things go off-script in such a beautiful way that they can't help but incorporate a gaffe into their movies. Even if that includes serious damage to their actors, or the destruction of irreplaceable artefacts.
1. Guardians of the Galaxy – Chris Pratt drops the ball
Star-Lord's butterfingers when offering the Orb to the Collector seem perfectly in character, but Chris Pratt really did drop the Infinity Stone. Luckily, he caught it, too.
2. The Outsiders – Diane Lane is only slightly amused
It was only too perfect for Matt Dillon's slimy Dallas to take a tumble when trying to flirt with Diane Lane's Cherry. But it wasn't in the script, which is why his castmates are genuinely struggling to stifle their giggles.
3. The Fellowship of the Ring – Mind your head, Gandalf
You can tell Sir Ian McKellen is a true professional as he managed to stay in character in the first Lord of the Rings film even after smacking his head on Bilbo's ceiling.
4. The Two Towers – Capture the flag
The flag flying from a pole in Edoras makes for a poignant symbol of the bad things to come for Rohan. But it was a happy accident – caused by the same strong winds that blew director Peter Jackson's glasses right off his face.
5. Titanic – Where do French girls go?
Leonardo DiCaprio found himself famously tongue-tied when inviting naked Kate Winslet to pose for a drawing. "All right, lie over there on the bed, uh, couch."
James Cameron liked it so much he decided to keep it in the film. "You know what was going through his mind," he said. Easy there, Jim!
6. True Lies – Jamie Lee Curtis needs to work on her sexy dancing
James Cameron clearly loves a blooper. This time it was Jamie Lee Curtis who took a tumble while performing the sex dance that has since colonised Giphy completely. You can see Arnold Schwarzenegger moving to help her, but Curtis leaps back to it like the pro she is.
7. The Hateful Eight – Farewell, priceless guitar
Quentin Tarantino was loaned a 19th century guitar for Jennifer Jason Leigh's outlaw Daisy Domergue to play in The Hateful Eight. A prop was provided for Kurt Russell to destroy... only for him to smash up the real, $40,000 one by mistake.
Leigh's horror on screen is genuine, and Russell was suitably mortified about obliterating an irreplaceable antique.
8. The Princess Bride – That's a knockout
The Princess Bride was sadly lacking in a prop sword, but Cary Elwes eventually goaded Christopher Guest to give him a 'gentle' tap on the head with his pommel. He woke up in the hospital, having been knocked unconscious for real. Luckily, one take was good enough.
9. The Usual Suspects – The one who smelt it
The lineup scene in Bryan Singer's crime thriller was supposed to be played straight, but the cast kept cracking up – allegedly because someone kept farting. Benicio del Toro said on a DVD extra that he didn't know the culprit, but his co-star Kevin Pollak has said that del Toro himself was to blame.
Singer wasn't impressed but eventually decided to embrace the giggling.
10. Rain Man – Farts: still funny
You will understand why Tom Cruise really wants to get out of that phone booth when you learn that Dustin Hoffman really did fart. Years later, Hoffman was still claiming that scene as the best moment of his acting career. What, better than Meet the Fockers?!
11. Blade Runner – Daryl Hannah suffers for her art
When Pris (Daryl Hannah) runs away from Sebastian in Ridley Scott's science fiction classic, she falls and puts her elbow through a car window. That was a real slip, caused by the rain-soaked ground, and it was later discovered that she had chipped her elbow in eight places. She still has a scar.
12. Annie Hall – Cocaine allergy
The fates conspired to cement Woody Allen's position as Hollywood's greatest nerd in Annie Hall. After being told that the cocaine passed around at a party is worth $2,000 dollars an ounce, he promptly sneezes it into oblivion.
Allen called it "a complete, unplanned accident", but test audiences found it so funny that he had to keep lengthening the sequence so that they wouldn't laugh into the next scene.
Bonus: Star Wars: A New Hope – Clumsy stormtrooper
We strongly suspect that the now legendary clumsy stormtrooper was included not because George Lucas thought it added to his movie, but because he didn't spot it. However, it has since been officially embraced, with Lucas adding a comedic sound effect to his remastered Star Wars.
