Since Bryan Singer's first X-Men movie was a surprise hit way back in 2000 — now nearly two decades ago, alarmingly enough — superheroes have been a frequent presence in the multiplex. Singer topped his first movie with the smashing X2: X-Men United, and Marvel's mutant squad has gone on to star in a total of six X-Men movies, two Wolverine spinoffs, Deadpool, and someday soon, The New Mutants. Spider-Man and Batman have both gone through multiple sequels and reboots, as has Superman. And when it comes to the Marvel Cinematic Universe, a franchise containing multiple franchises inside it, well...

But what about the superhero sequels that were planned, developed, and scripted, but for some reason never happened? Movies like a second Punisher with Thomas Jane, the Amazing Spider-Man's Sinister Six spinoff, and Tim Burton's third Batman were all in the pipeline at one time or another. Read on to find out what could have been with 15 Planned Superhero Movie Sequels That Never Happened.

(Remember, this is a sequels-only collection. Non-followups like Superman Lives and Justice League: Mortal do not count.)

15. Ang Lee's Hulk 2

Hulk

These days, the incredible Hulk is best known for his role in the Avengers movies, where Mark Ruffalo is either buddying around with Robert Downey Jr., or knocking down giant alien dragons with one punch. But back in the early days of the superhero revolution, Hulk was the subject of a love-it-or-hate-it arthouse film from Ang Lee, where the director of Crouching Tiger, Hidden Dragon attempted to do something dramatically different with the superhero genre. Though the film divided fans upon its release, both Lee and Oscar-nominated screenwriter James Schamus were already putting together plans for a sequel before the first one came out.

Not too much is known about the Hulk sequel that never happened, but Schamus did reveal that they were planning to have Banner transform into the grey Hulk (often called "Joe Fixit" in the comics) for at least a portion of the film. In the years since, Schamus has revealed that the sequel would have taken place on a Native American reservation, and would have been a politically-charged film that was going to be "all about radioactivity." Later on, of course, plans for a Hulk sequel were replaced by a reboot once Marvel got the rights back, though some traces of the original sequel concept remain in the finished film.

14. The Amazing Spider-Man 3

Peter Parker looks behind in Amazing Spider-Man 2

The phrase "don't put all your eggs in one basket" could have been created to describe what Sony did with its Amazing Spider-Man 2, the movie they were planning to launch an entire cinematic universe from. In one movie, they planted seeds for multiple others that would never come to fruition. One major part of this picture, of course, was going to be the third Amazing Spider-Man movie. We can likely assume that Norman Osborn would have probably played a role in it, given that Amazing Spider-Man 2 contained a deleted scene showing Norman's head having been cryogenically preserved.

However, comments by Captain Stacy actor Dennis Leary imply that the world may have escaped from the weirdest Spider-Man flick of all time. Evidently, the plot may have involved Peter Parker either creating or ingesting a formula that somehow would have regenerated all of the dead loved ones in his life, including Captain Stacy, and potentially Gwen, Uncle Ben, and Peter's parents. Hallucinations? Resurrections? A magic potion? Or perhaps, dare we say it, clones?

It sounds an awful lot like Amazing Spider-Man 3 might have been a loose adaptation of the Clone Saga, except with Peter's dead loved ones being cloned instead of him. It's not hard to imagine that this may have also been a way for Norman Osborn to come back, if his mind were placed within a cloned body. Would Scarlet Spider have appeared? The Jackal? Hard to say, but details will probably come out sometime in the next few years.

13. Sinister Six

The Sinister Six fighting Spiderman in Marvel Comics

However, what Sony was really banking on wasn't Amazing Spider-Man 3, but rather its plan to film a Suicide Squad-like movie all about the bad guys. The Sinister Six, a team of Spidey villains formed by Doctor Octopus in the comics, were set up and heavily teased at the end of Amazing Spider-Man 2. The team was going to include Harry Osborn's Green Goblin, Paul Giamatti's Rhino, Doc Ock, Vulture, Kraven the Hunter, and a widely debated sixth baddie (speculation ranged on everyone from Mysterio to Sandman for the final spot). Oddly enough, the movie was poised to be a redemption story for the villainous leads, and it's unclear whether Spider-Man would have featured in the film at all, much less whether he would've been played by Andrew Garfield.

While the film obviously got put on the shelf when Sony and Marvel brokered a deal for Spider-Man to join the MCU, a few bits and pieces escaped from leaked Sony emails. Director Drew Goddard was evidently courting Tom Hardy for the role of Sandman, and the movie was going to feature a conclusion wherein a Godzilla-sized Sandman rampaged through the streets of London.

While we have to imagine the Sinister Six will make their way onto the big screen at some point, the version we'll see will be very different from what was originally planned -- for better or worse.

12. Green Lantern 2

Movie Post Credits Scenes Green Lantern Sinestro

Back before Man of Steel, Warner Brothers were betting on the Ryan Reynolds-starring vehicle Green Lantern to be their next big superhero franchise, sculpting a film that imitated the Marvel Studios style but lacked the heart — and the wit. The movie clearly sets up Jordan's archenemy Sinestro to take a big role in a sequel, which they were planning to release in 2017.

The story treatment for Green Lantern 2, written before the first movie's release, had most of the sequel set to take place in outer space, and would have primarily revolved around Sinistro betraying the Green Lantern Corps to create his own, more sinister corps. The villain would also have kidnapped Carol Ferris, and the conclusion would have included setup for a "War of Light" that was supposed to take place in a theoretical third film. The first film bombed of course, and plans for sequels were scrapped in favor of a new shared universe kickstarted by this year's Batman v Superman.

11. Superman Returns Sequel

Brandon Routh in Superman Returns

Today, Bryan Singer's Superman Returns is best seen as the final movie of the Christopher Reeve series that began in 1978. But back when it came out, WB was hoping to use Superman's revival as the launching pad for a new series. That didn't work out, and Singer has since returned to his X-Men movies, but many details have emerged about Singer's cancelled plans for a sequel, which would've been titled Man of Steel, ironically enough.

The sequel would have begun by showing that New Krypton, the giant landmass that Superman threw into space at the end of Superman Returns, has evolved into a moon that Earthlings can see in the sky. This new moon attracts the attention of another surviving Kryptonian, who comes to Earth and is appalled that Superman, with all of his power, has done nothing to end mass starvation, to create world peace, and so on. This new alien proceeds to "fix" the Earth, winning worldwide acclaim.

However, it turns out that the new alien is actually just a humanoid guise for Brainiac, an artifical consciousness from Krypton, who was responsible for destroying Krypton and has now made Earth its next target. The finale would involve Brainiac transferring its consciousness into Jason, Superman's son, forcing the man of steel to choose between killing his son or saving the entire Earth.

10. Teenage Mutant Ninja Turtles IV: The Next Mutation

Teenage Mutant Ninja Turtles The Next Mutation concept art

Think the new Teenage Mutant Ninja Turtles movies are weird? Well, the plans for a fourth sequel in the original TNMT series were like anchovies on a pizza, as the concept art above demonstrates.

Back when TNMT III came out, producers were planning on a fourth movie called The Next Mutation, which would have involved all of the Turtles (and Splinter) undergoing secondary mutations. Donatello was going to develop telekinesis and telepathy (which would take away his eyesight), Michelangelo was going to be able to make himself look human, Raphael was going to morph into a deadly "Raptor Raph" form complete with sharp teeth and claws, Leonardo would have the ability to turn his skin into metal ala the X-Men's Colossus, and Splinter would be able to morph into a super-rat form so that he could have a bigger part in the battles.

Clearly, the studios thought that four mutant turtles weren't enough. There was also going to be a fifth Turtle named Kirby (after Jack Kirby, admittedly a nice touch), who was even drawn up for action figure concepts. The movie never happened, but its title was reused for a brief live action Turtles series in 1997.

9. Hellboy III

Ron Perlman on Hellboy 3 Kickstarter

Many are still hoping that this one will happen someday, but Guillermo Del Toro has said that it's unlikely that anyone will ever finance it, as he's already tried shopping it around to every studio out there. Still, he's also said that he's creatively interested in developing it someday, so there's a chance — a slight chance.

What we know for sure is a basic outline of what Del Toro was planning for the third movie, back when Hellboy II: The Golden Army was still fresh. As hinted at in the second movie, Hellboy III would have been about its title character becoming the "Beast of the Apocalypse." Hellboy and Liz were going to have to come to terms with his demonic destiny, and Hellboy was somehow going to have to accept this villainous role in order to defeat an otherworldly threat and save the human race.

Ron Perlman himself seems to have lost hope in the project though, so don't count on this one ever becoming a reality.

8. Punisher 2

thomas jane punisher superhero actor never sequel

Now that the Punisher has received such wide acclaim in the second season of Netflix's Daredevil series, it's hard to remember that any other cinematic versions ever existed. But back when Jonathon Hensleigh's Punisher movie came out in 2004, he and actor Thomas Jane were very interested in doing a sequel that would have picked up where the first movie left off, with an established Frank Castle taking on the scar-faced crimelord Jigsaw. The movie was set to come out in 2006, and Thomas Jane put on an additional 12 pounds of muscle for the role.

After multiple rewrites, Thomas Jane finally pulled out of the film, saying he wouldn't spend months of his life working for a movie he "didn't believe in." Later on, Lexi Alexander signed on as the new director, cast Ray Stephenson, and the movie was reworked into what eventually became Punisher: War Zone, a reboot instead of a sequel.

Ray Stephenson was attached to do a sequel to that film, but it never came together, and War Zone itself largely disappeared into the mists of forgotten cult movies. Instead, the Punisher rights expired and went back to Marvel Studios. The next time Punisher appeared it was on Netflix, his new home for the foreseeable future.

7. The Post-Apocalyptic Version of Blade III

Blade - Wesley Snipes - WWE Studios

After Blade II surpassed the first movie in tone, style, and action scenes, expectations were high for the third part of the trilogy. The disappointment was heard 'round the world when Blade: Trinity finally arrived, complete with bad jokes, a generic plotline, and an incarnation of Dracula that seemed woefully less threatening than the villains in the first two movies.

However, David Goyer's original vision for Blade III, which was unfortunately rejected by New Line, would have been an entirely different film. In order to close out the trilogy in an epic fashion, Goyer planned to have the movie open in a post-apocalyptic world ruled by the vampires. Humans were stuck into concentration camps and harvested for their blood, while Blade himself would have been forced underground by vampire domination. The story was shifted away from this in order to avoid comparisons to the then-in-development I Am Legend, resulting in the less interesting movie we finally got.

6. The 2015 Fantastic 4 Sequel

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Though the two Tim Story Fantastic Four movies weren't the most popular superhero movies around, they didn't inspire anything near the venom that was reserved for Josh Trank's 2015 reboot, an oddly dark, moody take on one of the brightest and zaniest comic books in history. 20th Century Fox had big plans for Marvel's First Family, with a sequel set to be released on June 9th, 2017. Though no official plot or casting announcements were made, there was even a lot of mumbling about Trank's version of the Fantastic Four eventually crossing over with Bryan Singer's X-Men, with 20th Century Fox looking to replicate Marvel's shared universe success.

After the movie absolutely bombed, Fox quietly pulled the Fantastic Four sequel from its schedule, and multiple cast members have stated they don't see it happening. The X-Men crossover hasn't been mentioned since.

Nowadays, Fox is devoting most of their energy to their abundant array of mutant properties, but at some point in the next few years, they'll have to decide whether they want to do a Fantastic Four sequel, do the origin a third time, or let the rights lapse back to Marvel Studios.

5. Dredd 2

Judge Dredd still

2012's cult classic Dredd, written by Alex Garland and starring Karl Urban as the title character, was everything that Stallone's poorly-received 1995 Judge Dredd was not: gritty, violent, and true to the tone of the comics, particularly in regard to the main character's face never being shown onscreen. Garland was upfront from the beginning about wanting to put together a trilogy of Mega-City One films that explored the notion of Dredd being a fascist, with the second movie delving into Dredd's origins, and the third introducing fan-favorite villain Judge Death.

Unfortunately, the first movie didn't gross anywhere near enough to get the studio excited, and Garland has said it's now unlikely to happen. Adi Shankar did produce an animated online spinoff series titled Judge Dredd: Superfiend, but so far that's the closest that a sequel has come to materializing. However, star Karl Urban hasn't given up hope, and he has promoted the idea of continuing the series via either Netflix or Amazon Prime.

4. X-Men Origins: Magneto

Magneto origin comic

If there's any one Marvel mutant that challenges Wolverine's popularity, it's the self-proclaimed master of magnetism. As a strong-willed character that fluctuates between villain and antihero but always grabs the audience's sympathy, Erik Lehnsherr has dominated the big screen since 2000. As a result, he would seem like a sure bet for a standalone movie, especially given his dark past as a victim of the Holocaust, and that's exactly what motivated 20th Century Fox back in the days of the original X-Men trilogy to develop X-Men Origins: Magneto.

Screenwriter Sheldon Turner wrote the script for a spinoff that he pitched as "The Pianist meets X-Men," with a story that would focus on the young Erik attempting to survive in Auschwitz, being liberated, forming a friendship with a young Charles Xavier, and then seeking vengeance on the Nazi war criminals who murdered his family. The movie was going to be bookended by sequences of Ian McKellen's older Magneto remembering his past.

Magneto was delayed by the 2007-2008 Writers Strike, and then put in stasis when the other prequel spinoff, X-Men Origins: Wolverine, had a less positive reception than expected. Luckily, much of the narrative tissue from the Magneto film was rescued and implemented into the movie that eventually became X-Men: First Class, with Michael Fassbender playing the young Erik.

3. Burton's Batman 3

Tim Burton's Batman 3 suit

One of the oldest "What if...?" questions in superhero movie history is the notion of what might have happened to the '90s Batman franchise had Batman Returns not scared parents so much, and had Tim Burton never been kicked off the series. The first two Batman movies -- though they make their share of divergences from the comics -- are drenched in Burton's trademark gothic style, which makes Schumacher's neon follow-ups seem incompatible with what came before (which is, as it turns out, the subject of an entertaining fan theory).

But there was a point where Burton could have directed Batman 3. A bit of pre-production concept work was done on an updated costume for Michael Keaton, and it's likely that Billy Dee Williams's Harvey Dent would have become Two-Face. Marlan Wayans, who was hired to play Robin in Batman Returns, was cut out of the film, but still contracted to appear in a third Burton Bat-movie. Bob Ringwood even did concept art design for a very gothic Robin costume that was dramatically different from the comics. However, the outcry after Batman Returns resulted in WB pushing Burton off the project, and going with the brighter Schumacher vision that became Batman Forever.

2. Schumacher's Batman Unchained

Batman and Robin

Joel Schumacher's Batman & Robin dropped a nuclear bomb on the Batman brand, which would only be revived roughly a decade later when Christopher Nolan brought the Dark k=Knight back to his roots in Batman Begins. But even back when Batman & Robin's wounds were still fresh — and kept frozen by an array of bad ice puns — WB wanted another sequel for one of its biggest franchises. And for a while, Schumacher was still attached.

Schumacher knew from the beginning that they needed to go in a more serious direction for the next movie, which would've been titled either Batman Unchained or Batman Triumphant . The script by Mark Protosevich cast Scarecrow as the villain, with a story involving Batman being doused with the villain's fear toxins and having to face his past demons in hallucinatory form, including cameos from Jack Nicholson's Joker, Michelle Pfeiffer's Catwoman, Jim Carrey's Riddler, and more. Harley Quinn would have also appeared, written in as the Joker's daughter. Teaming up with Scarecrow, the two villains would have locked the hallucinating Batman in Arkham Asylum.

This heavily psychological movie, in many ways the opposite of B&R, was targeted for a 1999 release. George Clooney and Chris O'Donnell would have returned, Nicolas Cage was offered the role of Scarecrow, and both Madonna and Courtney Love were rumored for Harley. The movie never came together, and WB instead pursued a Batman: Year One adaptation, which eventually evolved into the Nolan reboot that Bat-fans know and love today.

1. Spider-Man 4

Concept art for Sam Raimi's Spider-Man 4

The most unexpected reboot of all time was probably The Amazing Spider-Man, which came only five years after Sam Raimi's Spider-Man 3 failed to live up to its critically-acclaimed predecessors, but was nonetheless a box office smash. Sony immediately started developing a reboot, but allowed Raimi to develop a final movie in his series, which would have been Spider-Man 4, with Tobey Maguire and Kirsten Dunst both ready to come back.

Conscious of the fan disappointment in Spider-Man 3 and unhappy with the movie himself, Raimi pushed to make Spider-Man 4 "the best Spider-Man of them all." The film would have opened with a montage of Spidey defeating an array of villains, including the Rhino, Shocker, Prowler, and Mysterio, the latter of whom would have been played by Bruce Campbell. The movie's main plot would have featured Vulture as the primary antagonist, played by John Malkovich. Knowing that the audience were going to be expecting "an old guy in a silly green suit," Raimi and storyboard artist Jeffrey Henderson planned to, in Henderson's words, "go the opposite way and really make him the most fearsome and formidable adversary that Spider-Man had faced in the series." Anne Hathaway was also approached to play Felicia Hardy, the Black Cat, years before she became Catwoman for Christopher Nolan.

Eventually, the movie hit a deadline, and Raimi felt that to in order meet the deadline he would've had to turn in a movie that was less than great. Not wanting to repeat his disappointing experience with the third movie, Raimi instead stepped away from the project, telling Sony to go ahead and make the reboot that they were already planning. We'll never get to see the Spider-Man 4 that Raimi envisioned, but the storyboards that Henderson has released give us a vision of what could've been the grand finale of the Raimi series. Vulture, in the meantime, is rumored to be appearing in the upcoming Spider-Man: Homecoming.

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Which of these canceled sequels would you be interested in seeing? Which ones are you glad ended up on the chopping block? Let your voice be heard in the comments.