Regrets? We've all had a few. Most people's mistakes, however, aren't captured on camera for the rest of eternity. Pity, then, the red-faced actors and directors who have made films while quietly knowing that things weren't going the way they should.
Here are nine movies where the people in front of, or behind, the cameras have had to live with their mistakes making it into cinema history – and their thoughts on what exactly went wrong.
1. Spider-Man 3 (2007)
The mistake: Including Venom.
Hard as it is to believe now, two reboots on, but there was once a time when a Spider-Man big-screen outing was merely an unattainable Hollywood dream. Evil Dead creator Sam Raimi cracked it, making two films with warmth, humour and three-dimensional villains. And then he went and spoiled it all with Spider-Man 3.
There is such a thing as villain overload. The conflict with Harry Osborne (James Franco) had been methodically built up over the first two films and reached a head here. The Sandman (Thomas Haden Church), meanwhile, had the makings of a classic Spider-Man foe – as sympathetic as he was sinister.
Alas, Sony insisted that Raimi also include Venom (Topher Grace), a character beloved of many younger Spider-fans, but, crucially, not by Raimi himself. The character simply doesn't fit into the film and, worse, Peter's corruption by the black symbiote suit turns him from loveable dork into peacocking bell-end.
"I didn't really believe in all the characters," Raimi would later admit. "I think [raising the stakes] was the thinking going into it, and I think that's what doomed us."
And in case you've any doubts about what he thinks of the movie, he's since called it "awful".
2. Fifty Shades of Grey (2015)
The mistake: Giving the author too much power.
EL James' erotic novel Fifty Shades of Grey caused a sensation on publication, bringing S&M to Sainsbury's book shelves and boosting sales of rope, cable ties and duct tape to boot.
A film adaptation was a certainty, and Nowhere Boy's Sam Taylor-Johnson was hired to direct it, with a little help from the author... whether she wanted it or not.
Most novelists get only minimal say over how their work is adapted for screen. Not so James, who was granted a high level of power and wielded it over the director, allegedly quarrelling over every diversion from the original text, while demanding that screenwriter Kelly Marcel's script be rewritten to match the novel's – famously awful – dialogue.
Taylor-Johnson has spoken of "lots of on-set tête-à-tetes" with James, and that she's steering well clear of the sequel. "Would I go through it again? Of course I wouldn't. I'd be mad."
Of course, the final cut was a huge commercial success (despite getting a drubbing from critics who called it, amongst other things, "the Downton Abbey of bondage" and "50 shades of beige") so perhaps James was on to something after all.
3. Blade Runner (1982)
The mistake: Obeying the money men.
Ridley Scott's other science fiction masterpiece is 35 this year. Nowadays it's available in a plethora of different cuts, but audiences at the time only had one – with an infamously weak final scene.
The film's investors were unhappy with the bleak implications of the ending, which suggests that Rachael (Sean Young) is reaching her termination date and that Deckard (Harrison Ford) himself may be a replicant.
One of them told the director to insert an "uplifting" ending where the two escape to the country. Scott argued, "Well if they go off into a beautiful wilderness, why do they live in this dystopian environment?"
He was overruled.
An infuriatingly hand-holding epilogue was hastily assembled using spare location footage from The Shining and a flat voiceover from a plainly furious Ford. "Tyrell had told me Rachael was special, no termination date. I didn't know how long we'd have together. Who does?"
Thankfully, Scott has since excised it from the film, restoring the appropriately fatalistic edge he had planned.
4. The Hobbit trilogy (2012-2014)
The mistake: Too much haste.
Anyone would have a hard time living up to Peter Jackson's epic The Lord of the Rings trilogy – including, it turns out, Jackson himself. Originally conceived as two films, The Hobbit hit a rocky patch when director Guillermo del Toro quit the project, forcing Jackson to return to Middle-earth.
The Lord of the Rings was in pre-production for three and a half years before filming even started. Not so with The Hobbit.
"Because Guillermo del Toro had to leave and I jumped in and took over, we didn't wind the clock back a year and a half and give me a year and a half prep to design the movie, which was different to what he was doing," Jackson revealed in a frank interview on the Battle of the Five Armies blu-ray.
"It was impossible, and as a result of it being impossible I just started shooting the movie with most of it not prepped at all."
We'd like to say it doesn't show, but...
5. Diana (2013)
The mistake: Playing Diana.
Oliver Hirschbiegel's biopic of Princess Diana had the air of disaster about it from the off, but few would quibble with the casting of Oscar nominee Naomi Watts – a serious actress who brings credibility to any project (or any project not titled The Book of Henry, at least).
As the film was released to universally poor reviews, however, it became clear that the actress was unhappy, to say the least.
While Hirschbiegel has said he has no regrets about making the film, it's clear that his star has. Watts walked out of an interview with Simon Mayo while promoting the movie and has since referred to it as "a sinking ship".
She later told Harpers Bazaar: "I got seduced by the fantastic character. Ultimately there were problems and it ended up taking a direction that was not the one I was hoping for. With risk there is every chance it's going to fail." And fail it did.
6. Cannibal Holocaust (1980)
The mistake: Including footage of real violence.
This infamous Italian horror flick frequently shows up on lists of the most violent films of all time. Director Ruggero Deodato's tale of a documentary crew who fall prey to a man-eating tribe is arguably the first found-footage flick – and so realistic its director almost ended up in jail, after it was suspected he had really killed his cast.
He hadn't, but the film does include several scenes of genuine cruelty to animals.
There's no getting around it – the film is nasty. Monkeys, turtles and other animals are all shown being killed on camera. Deodato has said he regrets filming those sequences, justifying it by saying: "The death of the animals, although unbearable – especially in a present-day urban mindset – always happened in order to feed the film's characters or the crew, both in the story and in reality."
Recent edits of the film, however, have notably trimmed back some of these sequences.
7. Battlefield Earth (2000)
The mistake: Getting involved with Scientology in the hopes of getting a shag.
What more is there to say about Battlefield Earth? It's arguably the pinnacle of Hollywood folly and a film that prematurely tarnished John Travolta's resurgent post-Pulp Fiction career. The trash sci-fi flick, based on Church of Scientology founder L Ron Hubbard's novel, was an enormous flop.
And its screenwriter knew that it was going to fail.
In a 2010 essay for the New York Post entitled I penned the suckiest movie ever – sorry!, screenwriter JD Shapiro spilled the beans on what went wrong with the film. And it started with his motives for getting involved: he'd heard the Scientology centre was a good place to meet women.
After that, things got much worse when John Travolta's people began to tinker with his script.
"My screenplay was darker, grittier and had a very compelling story," Shapiro wrote. "They changed the entire tone... [Their] notes wanted me to lose key scenes, add ridiculous scenes, take out some of the key characters."
When he refused to comply, he was fired, leaving us with the glorious disaster we know and love today.
8. Star Trek Into Darkness (2013)
The mistake: Flat-out lying about Khan.
Before a single frame of JJ Abrams' second Star Trek film had been shot, fans were speculating that it might feature Khan Noonien Singh, the pneumatically-chested superman originally played by Ricardo Montalbán, as its big bad.
Not so, said JJ Abrams – Benedict Cumberbatch was playing a rogue Starfleet officer named John Harrison and not Khan. Definitely not. Honest.
Oh JJ, you big fibber. Half-way through the film Harrison, locked in a cell on the Enterprise, hisses "My name... is Khan!" Cue a fatigued sigh from fans worldwide – and a deep sense of irritation that they'd been lied to.
"I think it probably would have been smarter just to say upfront, 'This is who it is,'" Abrams has since admitted, while laying part of the blame at the studio door. "It was so important to the studio that we not angle this thing for existing fans. If we said it was Khan, it would feel like you've really got to know what Star Trek is about to see this movie. That would have been limiting."
Hmm. Now how about apologising for the lack of a colon in the title?
9. Rocky V (1990)
The mistake: Forgetting what Rocky is about.
The many Rocky sequels are of variable quality, but most are at least fun. Not so Rocky V, which supplants the robots and Russians of IV for a dose of grim reality as Rocky loses his hard-won fortune and ends up back at square one, re-opening Mickey's Gym and training up-and-coming fighter Tommy Gunn (no, no, not THAT one).
Sylvester Stallone – who, let us not forget, is the star of such legendary turkeys as Stop! Or My Mom Will Shoot and Rhinestone – has called the film, "Without a doubt one of the biggest disappointments in my life."
The series had reached its natural conclusion with IV and Balboa's defeat of Ivan Drago. Going back for one last round forced Stallone to take his beloved boxer to new, dour and joyless places – in this case brain damage, parental neglect and street brawls.
"The audience didn't want to see the downside of the character," he has since said. "They wanted him to remain on top. I should have known that. I fell into a sense of self-parody."
Happily, Stallone got to rectify the mistake with the superior Rocky Balboa in 2006, and again in 2015's terrific Creed – a far better take on the "Rocky as mentor" tale.