Films have a lot of input from a lot of people, and none which holds more authority than the demands from the heads of the studios.
After all, they're financing the whole thing, and they want to make sure their investment is going to reap dividends for them.
But sometimes their ideas fall quite wide of the mark of what audiences want to see.
Of course, when we say '12 famous films that were ruined by studios decisions' - the word 'ruined' is mostly for dramatic effect...
12. Blade Runner - change the ending and add more narration
Executive producers Jerry Perenchio and Bud Yorkin fired director Ridley Scott and producer Michael Deeley and took over the Blade Runner editing process themselves.
They felt viewers wouldn't understand the movie, so they got Deckard to add narration to explain the story.
Also, they changed the ending to make it end on a happier note with Deckard and Rachel driving off, editing in unused footage from The Shining.
11. Spider-Man 3 - add Venom to the already-packed story
Sam Raimi's idea for the third Spider-Man movie was to have a hero with negative qualities (black suit Spidey) and a villain with positive qualities (Sandman) while wrapping up the storylines of Mary Jane and Harry Osborn.
Enter Marvel producer Avi Arand, who convinced Raimi to include the character of fan-favourite villain Venom to the already heavily-packed plot.
Despite hating Venom (for his "lack of humanity"), Raimi shoehorned Eddie Brock and Venom - as well as Gwen Stacey - into the film, resulting in the lacklustre, trilogy-ruiner.
10. Dodgeball - have the heroes win the final battle
Originally the script was to have Peter La Fleur's underdog heroes lose the final round to White Goodman, but recover their losses thanks to a winning bet in Vegas.
Studio bosses forced the ending to be changed to have the heroes win the final.
This prompted director Rawson Marshall Thurber to purposefully hijack the ending, making the ending nonsensical, where Average Joes win the tournament AND the money.
In a scene during the end credits, White Goodman is moaning about his loss, stating that he only lost because "audiences can't cope with anything challenging."
9. The World Is Not Enough - replace a poignant ending with Denise Richards as a nuclear physicist and bad puns
The Bond movie was working on a poignant ending scene where 007 visits love-interest-turned-villain Elecktra King in a mental hospital to treat her Stockholm syndrome.
The storyline was dropped, instead going for a light-hearted 'classic Bond' ending, with Bond bedding nuclear physicist Dr Christmas Jones - played by Denise Richards - and the super obvious 'Christmas coming once a year' and 'unwrapping presents' puns.
8. I Am Legend - change the ending
When the ending of the Will Smith post-apocalyptic horror - based on Richard Matheson's 1954 novel - didn't go down well with test audiences, the studio knew they needed to make some tweaks to improve it.
The original ending had Will Smith's character Neville stuck in a trap and facing Darkseeker, who doesn't attack him, but resuces the female Darkseeker that Neville had been testing on.
This makes Neville realise that there is still humanity in the zombie-like creatures, and his attempts to treat them had been similar to that which created the Darkseekers in the first place.
The new 'Hollywood' ending sees Neville develop a successful cure and then blow up Darkseekers with grenades with a nice sequel hook to boot was panned by fans of the book.
The new ending creates large plot holes and foreshadows the twist ending which never arrives.
7. Daredevil - remove big chunks and give Elektra the spotlight
After early footage of Ben Affleck's Daredevil had been filmed, the executives at 20th Century Fox saw that Jennifer Garner's Elektra had potential as a spin-off movie.
They decided to take out vast swathes of the original script to give Elektra prominence and stick Daredevil's origins story in the back seat.
By removing a subplot about Matt Murdock defending a murder victim, it rendered Daredevil's ending confused.
To add insult to injury, Elektra didn't do very well in cinemas at all, resulting in both Marvel films missing the mark, and no sequels for anyone.
6. The Matrix - make the humans giant batteries
The Wachowski's original plan for The Matrix was to have the humans plugged in to the real world, with their brains forming a gigantic neural network computer.
Executives thought that audiences wouldn't understand the concept, so they changed it to humans being used as batteries to generate electricity - which is a scientific impossibility, as humans need more energy than they produce.
5. Old School - turn it into a 'frat house comedy'
Originally, Luke Wilson's 2003 comedy was written by Todd Phillips as a comedic parody of Fight Club.
At the time Phillips was writing the script, the studio thought that the film wasn't well known enough - as it had only been a box office flop and not the cult classic that it turned out to be.
Phillips had to rewrite it to be more like Animal House and his previous film Road Trip as an out-and-out college frat house comedy.
Original Fight Club aspects remain in the final film, such as Luke Wilson's character not having to pay at the local diner, and his work suffering as a result of his 'extra-curricular' activities, resulting in a showdown with his boss.
4. RoboCop (2014) - make it family-friendly to build a new franchise
Both director José Padilha and star Joel Kinnaman wanted the film to be as violent as the R-rated original cult classic, but Sony had other ideas.
They were keen to build a franchise similar to the Dark Knight Trilogy or Iron-Man films, so wanted it to have less edgier moments.
Padilha's explained working on RoboCop: "I have never suffered so much and I don't want to do it again" and for every ten ideas he had, nine were cut.
The reception was that the film missed out on what made the original special - all the violence that the execs chose to remove.
3. X-Men Origins: Wolverine - sew Deadpool's mouth shut
One of the most popular characters in Wolverine Origins, and in the whole comic book genre as a whole, Deadpool is renowned as 'The Merc with the Mouth'.
The executives at Fox presumably didn't want Deadpool to take the attention away from Wolverine, so quickly removed him after introducing him, then sew his mouth shut.
Director Gavin Hood often clashed with Fox executives on the production and revealed that portions of the script were being rewritten as the film was being made.
All-in-all it served to bring us (alongside The Last Stand) one of the worst X-Men films to date.
2. Prometheus - make the story vaguer and confused
Originally, Jon Spaiht had written a more direct Alien prequel named Alien: Engineers, with much more explanation about some of the more confused plot points, including supporting characters' motivations more clearly explained.
With more Xenomorphs, more intense scenes - like Watts' caesarean scene was going to have a chest-burster come out of her as she was preparing to perform the operation - and new types of xenomorphs.
Then 20th Century Fox brought in the 'named' writer - LOST's Damon Lindelof, who after success with the mind-bending desert island drama, convinced director Ridley Scott to dispense with the idea of an Alien prequel.
He then rewrote large swathes of the film to make it confused, confusing and downright disappointing.
1. Batman Forever - make it more family-friendly
Originally, Joel Schumacher's version of the caped crusader in Batman Forever was much darker, matching Tim Burton's previous films.
The execs at Warner Bros. extensively cut large sections of the film, which was originally close to two hours and 40 minutes in a bit to make it more family-friendly, in a bid to sell huge amounts of merchandise.
Fight scenes were dramatically shortened, a dark opening scene featuring Two-Face hanging his psychologist and Bruce regaining his memory thanks to a human-sized bat in the Batcave were cut as well.
Despite mixed reviews, the film scored big at the box office which meant that the execs thought they were right, and made the even more kid-friendly Batman and Robin, which ultimately killed off the franchise until Christopher Nolan rebooted it 18 years later.