Some of history's best films are sequels, like Terminator 2: Judgement Day or The Godfather 2, and sometimes we wish they'd have just left our favourite original films alone.
Here is a list of crazy sequels that we could have had, but fortunately sense prevailed and they never saw the light of day.
10. Gladiator 2
A previously-unseen script has been discovered for the Maximus follow-up written by musician and madman Nick Cave
Getting over the fact that Crowe's character dies at the end of the first film, Nick Cave's idea was that Maximus would be reincarnated by Roman gods, and made immortal.
The script sees the general-turned-gladiator fighting wars through the ages, including defending early Christians, leading tanks in WWII and eventually working in the Pentagon.
Russell Crowe and director Ridley Scott were really interested in the script, but the studio decided that it didn't work for them.
9. The Brazilian Job
A sequel to the 2003 remake of The Italian Job was developed, a script was adapted from an original screenplay titled The Wrecking Crew, but has since been put on the back burners.
According to producer Donald De Line, the plot "starts in Brazil, the setup is in Rio and the picture moves to Belgium where there’s something involving diamonds."
With lots of accounts confirming and denying whether it was going to happen or not, the talk has gone cold since 2010 and, despite having an IMDB page, it looks like it will never start shooting.
8. National Treasure 3
After the success of the original, and the moderate success of the sequel, Nicolas Cage was very interested in doing a third instalment of the adventure mystery films.
Producer Jerry Bruckheimer confirmed it was in the process, while in 2012, Cage explained that he would be interested in taking the series to South America.
By April 2014, Bruckheimer had declared that scripts had been written and the first act of National Treasure 3 was complete and exciting.
Despite that, there have been no developments since, so it looks like a third film won't be hitting our screens any time soon.
7. E.T. II: Nocturnal Fears
After the runaway train that was the success of E.T., Steven Spielberg and the movie's writer Melissa Mathison started work on a sequel.
Nocturnal Fears was planned to have evil aliens kidnap and torture Elliot, Gertie and Michael, with E.T. coming in at the very end of the film to save the day and banish the evil aliens to the other end of the galaxy.
Despite coming up with a nine page treatment for the sequel, Spielberg ultimately decided to not to continue with the film, stating his plan for the sequel "would do nothing but rob the original of its virginity".
6. Se7en 2 (or Ei8th?)
After the success of the dark, depressing serial killer thriller Se7en, New Line Cinema wanted to the repeat the formula, despite half of the main cast having been killed off.
That didn't deter the executives, as they took a screenplay from Ocean's Eleven and Matchstick Men writer Ted Griffin about a clairvoyant doctor who helps the FBI to catch a serial killer, and replaced the doctor with Morgan Freeman's character.
So in between the events of the first and second films, Detective Somerset would develop psychic powers to help solve cases.
Se7en director David Fincher read the script and said "it didn’t make a lot of sense" before later stating that he had "less interest in that than having cigarettes put out in my eyes.”
5. Gump and Co.
After being present for, and shaping, world history throughout the 1960s and '70s, what could be next for speedy simpleton Forrest Gump? Well, the story only just began in the first film.
Forrest Gump writer Eric Roth wrote a screenplay for a Gump sequel, which if it followed the events of the book, would feature such events as:
- The Bubba Gump Shrimp Company would suffer serious financial troubles and Forrest having to taking up a job as a janitor in a strip club
- Meeting an player for NFL team the New Orleans Saints and becoming a professional football player
- Sitting in the passenger seat of OJ Simpson's white Bronco in the famous police chase
- Accidently causing the fall of the Berlin Wall
- Fighting in Desert Storm with an orang-utan that he met when he was an astronaut.
Unfortunately for Roth, he submitted the night before the 9/11 attacks, and when Roth sat down with Tom Hanks and director Bob Zemeckis, they agreed that the screenplay wasn't relevant anymore, so decided to scrap the whole idea.
4. Double V Vega
Following the adulation that Quentin Tarrantino received for Reservoir Dogs and Pulp Fiction, he wanted to bring together two of the most interesting characters from each film, Vincent Vega and Mr Blonde, who was actually Vincent's brother Vic Vega.
More of a spin-off than a sequel, the plan was for a prequel with Michael Madsen and John Travolta, in which Vincent is in Amsterdam running Marcellus Wallace's club in the late '80s, when his brother Vic pays him a visit.
Unfortunately for the world, Tarrantino went straight onto Kill Bill, and then turned his attention to making Inglorious Basterds.
By the time he had finished working on those, Madsen and Travolta were too old to play the brothers in a sequel, and Tarrantino decided that it was best to let the idea pass him by.
3. Twins 2: Triplets
Twins has been a much-loved family comedy since its release in 1988, but the grumblings about a sequel have been going on since then.
One thing has been established, non-identical twins Arnold Schwarzenegger and Danny DeVito will discover they are triplets, with their third brother being... Eddie Murphy!
As recently as January 2015, Frozen's Josh Gad has confirmed that he has completed a script and sent it to Universal who are still deciding whether to make the sequel. So this one could still happen, imagine that.
2. Mrs Doubtfire 2
Up until the untimely death of Robin Williams, there were persistent rumours about him donning the female costume of Mrs Doubtfire.
Bonnie Hunt, Williams' co-star in Jumanji, was tasked with coming up with a script.
The screenplay was finished in 2006, but Williams branded it useless.
Despite no movement for the best part of a decade, the film was still being talked about until Robin Williams' death in August 2014, which cancelled the whole thing altogether.
1. Back to the Future 4 (and 5)
Riding high on the success of one of the 1980's finest trilogies, there was talk of making even more BTTF films, following Doc Brown's zany adventures through time.
Rumour has it that Men In Black and Bill & Ted's Excellent Adventure writer Ed Solomon was writing treatments for two a two-parter which would see Doc Brown accidently cause the infamous UFO crash in Roswell.
Instead of Marty, Doc would be accompanied by a young female scientist - the frontrunner for the role was said to be Sarah Michelle Gellar - to help put things right.
The BTTF team said they'd never do another film without Michael J. Fox, stating: “The idea of making another Back to the Future movie without Michael J. Fox — you know, that’s like saying ‘I’m going to cook you a steak dinner and I’m going to hold the beef. “You can’t do that."
On the subject of Back to the Future reboots and remakes, as recently as July 2015, the trilogy's director Robert Zemeckis vowed: "Oh, God no. That can’t happen until both Bob [Gale, his co-writer] and I are dead.
"And then I’m sure they’ll do it, unless there’s a way our estates can stop it."