Text (for context) and a deleted footnote (the fun part) from the methodology chapter of my dissertation, currently in development:
Superhero comic book culture itself recognizes its own media situation: the Marvel Comic Universe is sometimes, in fandom particularly, referred to as Earth-616, while the Cinematic Universe is conceived of as an ‘alternate dimension’—a variation rather than a derivation—known as Earth-199999.
 This is an intentional distinction on the part of the content creators, but the discursive situation is further complicated by other factors, such as business and politics. For instance, the Spider-Man and X-Men films do not exist in nor recognize the continuity of the Marvel Cinematic Universe–or each other, for that matter–yet they nevertheless stand in an identifiable proximity to the same Marvel Comic Universe that provided their origins and which, through the assignment of designation numbers, both recognizes them and reserves some potential for mounting future narrative mergers and crossovers featuring them. Their designations are as follows: the Spider-Man series beginning with 2002’s Spider-Man is denoted as ‘Earth-96283’, while the ‘reboot’ is known as ‘Earth-120703’, effectively validating the concomitant canonical existences of both: according to Marvel, both are Spider-Man. The X-Men series, beginning with 2000’s X-Men and extending into the Wolverine franchise constitutes Earth-10005 (though others, such as 2016’s Deadpool and 2017’s Logan, occupy Earth-TRN414; the new television show Legion, meanwhile, takes place in another X-Universe offshoot, Earth-TRN620). Interestingly, the Marvel Database (Marvel.wikia.com) lists the original X-Men film universe, Earth-10005, as ‘destroyed’, due, narratively-speaking, to the timeline-bending events of its ‘last’ film, Days of Future Past, itself a plotline culled from the 616 universe. But it doesn’t end there, the complexities of licensing have also given us, among others, Earths 121698 (beginning with 2005’s Fantastic Four film), 400083 (2003’s Hulk, as opposed to the iteration of the character that appears in the Marvel Cinematic Universe’s Avengers films, part of the aforementioned 199999), 92131 (cartoons such as X-Men: The Animated Series), 58627 and 58732 (the 1989 and 2004 Punisher films), and even 58470 and 58472 (the Howard the Duck film and its own subsequent comic book adaptation, respectively; ‘58471’, oddly, has no listing).
Our own material reality is designated as Earth-1218, but we also inhabit what Marvel calls the “Omniverse”, which itself comprises:
“every single universe, multiverse, dimension (alternate or pocket) and realm. This includes not only Marvel Comics, but also DC Comics, Image, Dark Horse, Archie, Harvey, and every universe ever mentioned or seen (and an infinite amount never mentioned or seen)…. The Omniverse is EVERY reality, including those published by all other companies. Even fan-fictions, cancelled works, mere thoughts created by people, and fictional universes yet to be published are considered part of the Omniverse, simply put the Omniverse is every version of every type of reality and existence imaginable.”