Eight years after purchasing Marvel Entertainment and five years after buying Lucasfilm, The Walt Disney Company is considering acquiring many of the entertainment assets of 21st Century Fox, which could unite every Marvel movie superhero under one banner for the first time.

According to CNBC, the two companies have been discussing the deal “over the last few weeks,” while Bloomberg reports that talks have stalled and a deal may not be reached. The negotiations reportedly began because Fox wants to scale back its operations to focus more on news and sports. The company believes that Disney has the reach and resources that Fox does not; in fact Disney is already dreaming up its own streaming service after the studio announce it was ending its deal with Netflix earlier this year.

The Fox sale would not include properties like the Fox broadcast network (Disney already owns ABC), Fox Sports (Disney already owns ESPN) or Fox News (because who would want to buy it?). It would, however, include Fox-owned cable networks like FX and National Goegraphic as well as international TV properties like India’s Star and some stake in Sky in Europe.

The implications of such a deal, should it actually happen, are vast, but let’s focus on the most lucrative prospect: the merging of superhero universes. For decades, Fox has held the rights to two of Marvel Comics’ most famous properties, X-Men and the Fantastic Four. Marvel’s group of mutants, the most popular comics franchise in the world from the late 1970s to the early 1990s, has spawned 10 films with varying degrees of success, including Logan (Hugh Jackman’s curtain call as the character Wolverine) and Deadpool, both of which were two of the best-received superhero films as of late. The Fantastic Four have had considerably less success over the course of three films and one disastrous reboot, leading to frequent cries from fans for Fox to sell the characters back to Marvel Studios. At the moment, the X-Men movie universe is developing a Deadpool sequel, a New Mutants movie, a Gambit spinoff and the latest film under the main X-Men banner, Dark Phoenix. Fantastic Four is still waiting to be resurrected yet again.

Let’s say this happens or that at least some version of it does. Marvel already reached a co-production deal with Sony that allowed them to reboot Spider-Man and incorporate him into the Marvel Cinematic Universe. This is different, though. The Fantastic Four are one family with their own massive group of supporting characters and supervillains. The X-Men are a cast of hundreds. What if all of that lands in the lap of Marvel Studios, a company that’s already built the most complex and successfully ($13 billion and counting) superhero universe in the history of cinema?

Fox’s X-Men movie-verse is not as large as Marvel’s, but it’s certainly been around longer—almost a decade longer, in fact. Marvel Studios president Kevin Feige was helping to produce those films well before Iron Man or The Avengers ever dreamed of getting off the ground. It’s got its own famously tangled timeline and cast of characters spanning decades of continuity. More importantly, it has name huge billings already, with Patrick Stewart, James McAvoy, Ian McKellen, Michael Fassbender, Jennifer Lawrence and Ryan Reynolds. That universe has certainly had considerable success with recasting and retconning at this point (remember when Mystique was played by Rebecca Romijn?) but what happens if it all lands at Marvel? You can’t those narratives took place in the same universe as Marvel’s. If so, why didn’t Captain America show up when Apocalypse was destroying the planet? Why didn’t Howard Stark and S.H.I.E.L.D. come in to intervene during the X-Men’s involvement in the Cuban Missile Crisis? It’s simply too much to explain in throwaway dialogue.

That leaves us with two basic options. You either wipe the slate clean, recast the characters and hope your brand is strong enough to carry that weight or you introduce the idea of a multiverse into your already complicated cinematic timeline. You say, “Oh, all of that happened, just on a parallel Earth and now there’s gonna be an incursion” or “Hey, we love those old movies, but this is the new Wolverine and the new Professor X and the new Magneto.”

Both approaches can work. The multiverse is a time-honored comic book storytelling trope, but the latter seems more likely. It’s already worked for Spider-Man, and even if it’s not Hugh Jackman donning the mutton chops, who doesn’t want to see Wolverine and Hulk together at last? Of course, the company still has to contend with all of the Fox X-Men films currently in production, plus two TV shows, Legion and The Gifted, but they could simply wait three years before introducing the new characters. Marvel’s not going away anytime soon, with films booked through 2021.

By the way, the Fantastic Four present a far less complicated solution: just pave over it with a clean slate, new cast and a world where Tony Stark and Reed Richards finally get to have a meeting of the minds. Of course, this all purely hypothetical since the deal is not finalized. If it happens, though, it would likely blow up the box office like we’ve never seen before—and make DC cry.