With six mainline X-Men movies, three Wolverine spinoffs, and Deadpool behind us, with another four movies on the way (New Mutants, Dark Phoenix, Deadpool 2, and Gambit), plus two TV series, the X-Men franchise is one of the cornerstones of American superhero media. For all that, there's been a lot of speculation on what could have been. The reboot that started with First Class brought with it a host of predictions and wishlists when it became clear that the entire cast was being replaced. When Deadpool teased Cable in the sequel with an after-credits scene, the internet exploded with theories. As rumors swirl that Hugh Jackman will finally retire after 17 years and seven movies as Wolverine, who will replace him is a question on everyone's mind. But it's not the only one.

RELATED: 15 Supervillain Fan-Casting Photoshops Way Better Than What We Got

This list is a look at a world that might have been, a Days of Future Past alternate history where things went a little differently in various casting directors' heads. Some of these entries are for movies that haven't come out yet, but the roles have already been cast and we've already seen promotional images of the characters.

15 THE ROCK AS APOCALYPSE

the rock apocalypse

X-Men Apocalypse was, frankly, kind of disappointing. Another round of Magneto waffling between hero and villain, another disappointing villain, and another episode of the "Mystique is the real hero" show. There's probably not a lot that could balance out the mediocre script and acting, but if anything could, Dwayne "The Rock" Johnson playing Apocalypse to the full bombastic hilt would be it.

While this photoshop decided to give him a comically huge neck for some reason, picturing a hulking Apocalypse towering over his horsemen and the X-Men presents a far better (and more comics-accurate) image than average-height, average-build Oscar Isaac. And of course, someone somewhere thought The Rock was appropriate to play an Egyptian supervillain, as evidenced by his casting as Captain Marvel villain Black Adam.

14 TOM HARDY AS WOLVERINE

tom hardy wolverine

With Huge Jackman's time as Wolverine coming to a close with Logan, speculation runs rampant as to who will replace him as the iconic angry Canadian mutant. Already seasoned in superhero films with his turn as Bane in The Dark Knight Rises, he even has a pedigree to replace Jackman, having portrayed an Australian in Mad Max: Fury Road. Even Jackman himself wants Hardy for the role.

Hardy certainly has the acting and action movie chops to take the place of the ol' Canucklehead, and is certainly a big enough guy for us to support his casting. Whether he can live up to Jackman's 17-year run on the character is another story, and whether there are even enough Wolverine stories to tell after six movies is yet another wrench in the works.

13 SCARLETT JOHANSSON AS EMMA FROST

scarlett johansson emma frost

Making her cinematic debut in X-Men First Class, the White Queen of the Hellfire Club was, disappointingly, almost a complete non-entity. January Jones, normally a strong performer, played the part a little too far into "ice queen," with none of the haughty, sarcastic and sexual character from the comics on display, reduced to little more than a prop and plot device. A large part of that is on the script, of course, but Jones also dropped the ball on what could have been a truly breakout performance.

Johansson, on the other hand, is a tried-and-true superhero actor, and while First Class came a year before Avengers, her continued excellence in the MCU shows that she's comfortable in a superhero universe, while Jones clearly was not. Even further, her work in things like Lucy and Ghost In the Shell show that she can work with a bad script.

12 DANIEL CRAIG AS MAGNETO

daniel craig magneto

There's no denying Michael Fassbender has done a fine job as Magneto, and Ian McKellen in the role is virtually untouchable. However, with Daniel Craig leaving behind the role of James Bond, and Michael Fassbender expressing an interest in the role, maybe it's time for a swap? Few actors can match Craig's on-screen charisma, and he would certainly bring new life to a role that has already fallen into rote as Magneto has, just as he did for Bond.

Although it's unlikely Craig will step into the role of Mutant Master of Magnetism, if or when Fassbender steps into Bond, there are other X-Men casting rumors surrounding Craig, namely that he is in talks to play Victorian villain Mr. Sinister in the upcoming Gambit movie.

11 DIANNA AGRON AS POLARIS

dianna agron polaris

Lorna Dane is Magneto's third child, after Pietro and Wanda Maximoff (although recent comics developments may mean she is now Magneto's only child). Inheriting her father's mutant mastery of magnetism, she's something of a bit player in the main X-Men story, usually relegated to spinoffs that end up better than the main series like X-Factor, and, in the live action universe, spinoff TV series The Gifted.

While The Gifted is off to a strong start, and Emma Dumont is putting in a strong performance as Lorna, it's no X-Factor. Dianna Agron is probably the best thing to come out of the teenage nightmare that was Glee, and she could certainly hold her own as the green haired Mutant Mistress of Magnetism; perhaps as an older, more experienced version compared to Dumont's.

10 CHARLIZE THERON AS MYSTIQUE

charlize theron mystique

Mystique in the X-Men franchise has gone through some pretty drastic changes across the 17-year run of movies. Starting out with Rebecca Romijin's almost-silent body-painted villain, the role moved on to an actual plank of wood, who had a star-making turn as a more morally ambiguous protagonist. While both performances have their merits, neither really live up to the comics or even the cartoon version of X-Men Evolution.

Charlize Theron, on the other hand, is unafraid to be sexy, unafraid to play the villain, has quite a bit of experience in action films, and most importantly, isn't an actual plank of wood. With the possibility of the X-Men film universe moving away from a single narrative and into several different storylines across multiple time periods, there's certainly a place for an older, non-wooden Mystique.

9 MORENA BACCARIN AS DOMINO

morena baccarin domino

This one is a little more of a plot speculation (since disproved) than a wishlist. Morena Baccarin of course played Deadpool's love interest Vanessa Carlysle in Deadpool, but upon the announcement that mutant mercenary Domino would appear in Deadpool 2, speculation swirled as to who would play the longtime X-Force member. One popular theory was that Baccarin's Vanessa would become Domino to match Wade Wilson's change into Deadpool.

Although Atlanta's Zazie Beetz was eventually cast in the role and will probably turn in an excellent performance (although her costume and makeup is a little disappointing to some fans), Vanessa in the comics is in fact a mutant with the power to copy others' powers. This leaves some window open for Vanessa (and Baccarin) to become a second Domino.

8 JENNA DEWAN TATUM AS ROGUE

With Gambit barreling down the pipeline, and with Anna Paquin seemingly out as Rogue pretty definitively, theories once again begin to fly as to who will play the Ragin' Cajun's most famous love interest. Since Channing Tatum is already confirmed to play Gambit, it seems fairly obvious to cast his real-life actress wife as Rogue, not least because this image looks really good.

Pre-baked chemistry is probably the strongest argument, but Dewan Tatum also already has some experience with live-action superheroes, playing Lois Lane's younger sister Lucy Lane on CW's Supergirl. Although there's no confirmation that Rogue will appear in Gambit, the filmmakers would be foolish to pass up an opportunity like this, and it could certainly open the door to reintroducing Rogue into the larger franchise.

7 LUPITA NYONG'O AS STORM

lupita nyongo storm

When Storm was announced to appear in X-Men Apocalypse, the fandom train hopped right on the speculation. Lupita Nyong'o quickly emerged as a fan favorite for Storm, having become a household name since her relatively recent success on the big screen.

After some surprisingly (or maybe not so surprisingly) racist reasoning as to why and why not Nyong'o would be perfect/terrible for Storm, the role was eventually cast with Alexandra Shipp, who went on to be the best new face in the film. It would have been interesting to see Nyong'o as a slightly older Storm, but fortunately we'll get to see her take another superhero universe in the upcoming Black Panther, wherein she plays Nakia, one of the titular hero's Dora Milaje, or personal guard.

6 CLINT EASTWOOD AS OLD MAN LOGAN

clint eastwood wolverine

When Logan was announced, speculation ran rampant that it would be an adaptation of Mark Millar and Steve McNiven's Old Man Logan. While these theories were eventually confirmed, fans still wondered if Hugh Jackman would continue to play Wolverine, or if an older actor would be brought in. Among these theories was Clint Eastwood, well known for playing grumpy and growly old men.

While Eastwood is well past his action movie prime, he's still an accomplished actor, and it would have been interesting to see a Wolverine that has lived so long as to actually age significantly. It would also have brought the movie more in line with the comic it loosely adapted, which sees Logan in a future pretty significantly different from our own

5 LILY COLLINS AS SCARLET WITCH

lily collins scarlet witch

Wanda Maximoff, the Scarlet Witch. has thus far been an almost-non-presence in the X-Men movies, with a possible cameo as Quicksilver's much younger sister in Days of Future Past and a reference to her in Apocalypse. However, there has been no official confirmation that this character is Wanda, or if she even exists in this universe at all. She has, however, established herself over in the Marvel Cinematic Universe, played by Elizabeth Olsen.

Lily Collins is a relatively unknown British actress, but after turning in a powerful performance in To the Bone, she certainly has demonstrated that she has talent and the capability to play a troubled young woman, much in the vein of Scarlet Witch and her many, many mental health issues. She could certainly bring the final missing piece of Magneto's family to the big screen.

4 THOMAS KRETSCHMANN AS NIGHTCRAWLER

thomas kretschmann nightcrawler

Nightcrawler is one of those really popular characters that never gets enough justice in the movies. Vanishing from the original X-Men trilogy after appearing in X2 played by Alan Cumming, and reappearing younger for X-Men Apocalypse played by Kodi Smit-McPhee, he's never quite landed in the public consciousness to the same degree as Storm or Wolverine. While Smit-McPhee is unlikely to be replaced for Dark Phoenix, there is still a possibility of X-films focusing on older X-Men later in the timeline.

Thomas Kretschmann is an excellent German actor probably best known to American audiences for playing Baron Wolfgang Von Strucker in Captain America: The Winter Soldier and Avengers: Age of Ultron. Between experience in superhero films, a fine acting pedigree, and being German, he seems like a natural fit for Nightcrawler.

3 SUMMER GLAU AS X-23

x-23 summer glau

Logan introduced Wolverine clone and fan-favorite ass-kicking girl Laura Kinney, better known as X-23, to live action. Originally created for the X-Men Evolution cartoon, she made the jump to comics in NYX as a lady of the evening, written by Marvel's current Chief Creative Officer Joe Quesada. While Logan showed X-23 as younger than she'd ever been portrayed, fans speculated on an older X-23, more in line with her comics counterpart.

And who better than ass-kicking waif extraordinaire Summer Glau, cult famous for her turn in Firefly, and then proceeding to play basically the same character in every appearance since. She certainly has the action-star chops to play the role, and X-23 certainly fits into the mold of characters she's played in the pas. And of course, an older X-23 would certainly be interesting to see, and a huge deal for her fans everywhere.

2 RINKO KIKUCHI AS DOMINO

rinko kikuchi domino

With Domino confirmed for Deadpool 2, fans started speculating. One wishlist included Rinko Kikuchi. Best known to Western audiences for her role as Mako Mori in Pacific Rim (to be reprised in the upcoming sequel Pacific Rim: Uprising), Kikuchi has had a pretty long career in Japan, showing herself to be an accomplished and talented actress in multiple languages.

The photoshop also just really evokes that sort of punk-ish aura that Domino can find herself with as well, even though it's a fairly simple addition. Her performance in 47 Ronin as the morally ambiguous mercenary Witch also provide a strong argument for her capability to play equally morally ambiguous mercenary Domino. While actual Domino Zazie Beetz is a talented actress, she doesn't have nearly the same breadth of experience as Kikuchi.

1 KEIRA KNIGHTLEY AS CABLE

keira knightley cable

Let's be real, this is the best one on the list. Springing out of an after-credits teaser of Deadpool, Deadpool teased that Deadpool 2 would include Cable, and jokingly hinted that Keira Knightley was being considered. While obviously the casting department for Deadpool 2 didn't follow through on the joke, casting Josh Brolin as Cable, can you imagine if they did?

What if they went all in and cast a major character in a superhero action movie based entirely on an after-credits joke? Knightley playing post-apocalyptic future mutant savior Cable to the hilt in all his gruff and grim '90s poster boy glory would have been amazing! One of the most petit actresses in Hollywood playing a character popularized by Rob Liefeld would also have been quite a coup! People wouldn't even be mad that they gender-bent Cable. Okay, they would, but who cares about them?

Which other fan-casting photoshops have you seen that would rule? Let us know in the comments!