Spider-Man: Far From Home may be setting up the Captain Britain Corps. in the MCU (or at least one dimension of it). Marvel has been carefully developing the idea of the Multiverse since 2013's Thor: The Dark World, and the concept played an important part in both 2016's Doctor Strange and this year's Avengers: Endgame. According to the latest Spider-Man: Far From Home trailer, it's also key to the latest adventure for Peter Parker.
In the trailer, Mysterio claims that the events of Avengers: Endgame tore a hole in the fabric of reality, and that he actually originates from a parallel universe. A new clip has fleshed out his claims a little, with Mysterio dubbing the MCU "Earth-616" and claiming to originate from Earth-833. What's more, if Mysterio is really being honest, he seems to be quite familiar with dimension-jumping; he even notes that Earth-616 and Earth-833 "share identical physical constants, Level 4 symmetry."
Right now, it's impossible to say whether or not Mysterio is truthful, of course. In the comics, he's best known as a supervillain illusionist who revels in falsehood and manipulation, so it's hardly inconceivable that the whole thing is a stunt. For all that's the case, though, Nick Fury is a pretty hard man to fool, and it's undeniable that the best lies are half-truths; there's a surprising comic book precedent for Mysterio being able to traverse the Multiverse, so him lying needn't mean the whole idea is out.
Regardless, assuming Mysterio is telling at least a half-truth, the reference to Earth-833 is surprisingly important; it could well prepare the way for the MCU to introduce the Captain Britain Corps.
Captain Britain Corps. Are Why Mysterio’s Reality Doesn’t Have A Spider-Man
Mysterio seems quite taken with Spider-Man, and in the Spider-Man: Far From Home trailer he expresses the wish that his world had a hero like Peter Parker. This clearly suggests that, however similar Earth-833 is to the MCU, it doesn't have a Spider-Man. Surprisingly, this actually fits with the comics; Earth-833 is a parallel reality in which it wasn't Peter who was bitten by a radioactive spider - it was one William Braddock. Rather than become Spider-Man, the British superhero was swiftly recruited by the multidimensional Captain Britain Corps. He left his own universe in order to become an interdimensional hero, taking up the codename "Spider-UK," and he never returned to it.
It's surely no coincidence that Marvel chose to reference an alternate Earth in which there really wouldn't be a Spider-Man. At the same time, though, this goes one step beyond that; it subtly implies the existence of the Captain Britain Corps. in what we should perhaps be beginning to call the Marvel Cinematic Multiverse.
In the comics, the Captain Britain Corps. are essentially a group of interdimensional first responders, and their remit is to step in whenever the Multiverse itself is threatened. They were created by comic book writer Alan Moore and artist Alan Davis back in 1984, a group they envisioned as having been formed by the sorcerer Merlyn, his daughter Roma, and Sir James Braddock. Merlyn considers himself to be the Omniversal Guardian, and to that end he manipulated events so as to create a "Captain Britain" equivalent in every reality; he then recruited each version of Captain Britain into a loose army to protect the Multiverse.
Marvel May Be Building Towards A Captain Britain
For several years now there have been intermittent rumors that Marvel Studios is interested in a Captain Britain film. Back in June 2017, Kevin Feige openly noted that Marvel were considering the idea; "We have discussed it," he noted. "There are a lot of actors that come in and ask us about that part, so we'll have to see." In September 2018, unconfirmed reports suggested Marvel's plans had developed somewhat, and they were working on a Captain Britain and the Black Knight movie to be helmed by Guy Ritchie.
Avengers: Endgame may have even established Captain Britain in the MCU. When Steve Rogers and Tony Stark traveled back to 1970 in order to steal Pym Particles and the Tesseract. Steve found himself hiding unwittingly in the office of then-S.H.I.E.L.D. director Peggy Carter, and eavesdropped her talking about liaising with someone named "Braddock." There's only one Braddock family in Marvel; the family of Brian Braddock, a.k.a. Captain Britain. Whether this was Brian or his scientific genius father James is unclear, but it means Spider-Man: Far From Home's Earth-833 reference is the second consecutive MCU film to nod towards Captain Britain.
How Could The Captain Britain Corps. Fit Into The MCU?
If Mysterio is correct when he at least says Thanos' snap has opened the MCU up to the wider Multiverse (even if he's not from it), then representatives of the Captain Britain Corps. would logically be dispatched to investigate. Frankly, given the Avengers' actions created and then apparently cauterized multiple alternate timelines, it's reasonable to assume the MCU's Earth-616 would already be on their radar. Any escalation - say, a tear in the fabric of reality and beings literally jumping from one Earth to another - would inevitably lead the Captain Britain Corps. to check the source of the disturbance out.
The concept of the Multiverse really does look set to be central to Marvel's future plans, and the Captain Britain Corps. could easily be a key part of it. They have the advantage of being superheroes who are entirely used to the idea of the Multiverse, and thus can both explain it and navigate it with ease. In the comics, they're based at the Starlight Citadel, a tower of infinite portals to different dimensions, that exists in a plane of reality called Otherworld. The MCU could easily switch this up a little, with the Starlight Citadel instead set in the Quantum Realm. Indeed, Ant-Man & the Wasp included a brief, blink-and-you'll-miss-it glimpse of a mysterious city in the background of the Quantum Realm, one that could easily be the MCU equivalent of the Starlight Citadel.
If that's the case, then in Avengers: Endgame the Avengers unwittingly stumbled on the kind of science and technology that the Captain Britain Corps. have been using for generations. But the Avengers were just gifted amateurs, and Endgame went to great lengths to stress that they were winging it; the Captain Britain Corps. are the professionals. They'd be ideally suited to establish the basic rules that underpin the MCU's version of the Multiverse, straightening out the somewhat messy and unclear situation that's been left by the latest Avengers blockbuster.
Whether through a Captain Britain movie or as part of an Avengers 5, the introduction of the Captain Britain Corps. would mean establishing a set of heroes - and, of course, Captain Britain's villains - who can jump between the dimensions at will. The Multiverse would be opened up for future exploration, with the Captain Britain Corps. at the heart of it.
