Scratch a comics fan in the late 80s or early 90s, and you would find someone who had strong opinions about DC Comics continuity. In a complicated and ultimately pointless effort to create a single coherent cosmology out of a comics line that had been going on for decades and included the acquisition of several other publishers, DC writers created a universe with dozens of alternate earths, most notably Earth-2, which contained the 1940s-era heroes of the Justice Society. By the 80s, no one had any idea what was going on, and DC destroyed the multiverse in a giant year-long crossover, Crisis on Infinite Earths. And then brought it back again. And then destroyed it again. And then … well, suffice it to say DC’s multiverse is one of those weird things about comics that non-readers will never really know about.
Or maybe not! The opening of the second season of The CW’s Flash TV series introduces not only Earth-2 (although quite a different Earth-2) but the character of Jay Garrick, the Golden Age Flash. And not just an alternate-universe plotline, but the whole bit, right down to recreating the famous cover of 1961’s Flash #123, the story that introduced Earth-2. This doesn’t mean we’re going to get a precise recreation of the Multiverse or its modern equivalent, but it does mean that the possibilities for enemies, new characters and new adventures just multiplied.
From a comics-adaptation perspective, this makes sense. Probably no DC character is more closely associated with the multiverse than the Flash, and you lose a lot of potential storylines if you just ignore the multiverse. It looks like the creators are banking on a fanbase being willing to accept complicated metaphysics — Fringe worked, after all — in exchange for the story possibilities of the concept.
Of course, we don’t know what’s going to come of Flash‘s multiverse; it’s already different from the comics version in a number of ways, and it’s probably only going to diverge more. Still, this is only the latest in a series of decisions Flash‘s creators have made to draw heavily on the more implausible aspects of the character’s history (as opposed to Arrow, which initially at least seemed a little reticent about its own superheroic origins).
The last decade of superhero movies and TV shows are like this in a lot of ways, actually — you can see studios and networks replicating the decisions that comic publishers have already made. Got a set of popular superhero characters? Combine them into a team! Want to boost a flagging franchise? Guest appearance! Need to shake up your status quo? Crossover event! And now, apparently, multiverses — although this multiverse isn’t an effort to resolve confusing continuity problems. Maybe that means it’ll actually make sense?