The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction and denies the actuality of wavefunction collapse. Many-worlds implies that all possible alternate histories and futures are real, each representing an actual "world" (or "universe"). In lay terms, the hypothesis states there is a very large—perhaps infinite[2]—number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes. The theory is also referred to as MWI, the relative state formulation, the Everett interpretation, the theory of the universal wavefunction, many-universes interpretation, or just many-worlds.
-Wiki
So after many attempts at getting a justice league game running on various forums with little payoff. I believe I've found something that's worth sticking to. Basically, the idea I want to explore with this one is the idea of the multiple universes or multiverse, in essence, infinite character possibilities, you can be any leaguer (canon, original, or other) based on any alternate DC world (anything from DC comics/tv media) or go completely original, it's up to your discretion really, just be able to explain the nature and basic premise of the universe your character is from. This is loosely based on the convergence book event, which involved a story centered around multiple one-shot worlds, you don't have to be at all familiar with the source material to make a character, however some understanding of the multiverse story might help with some ideas for concepts if you're needing a reference. You want to be a zombie flash? Ok? Nazi Super-woman? Also ok. Anything is possible in the context of the multiverse.
You want to do an original with a faceclaim from other media who for some reason is connected to a justice league character in some way? That's also fine I guess. Villains are also acceptable.
What's important is you understand what this roleplay is and isn't about. Think of a justice league composed of many different members from many different alternate realities. Each one as distinct and unique as the one before.
In some world, somewhere... someone like the The Joker is actually a good guy. Some food for thought.
So I wanted to do justice league, but in a way that hasn't been done before. One Justice League. Many Worlds, Many Timelines. Infinite character possibilities, or you can just stick to the mainstream counterparts if those ideas don't work for you. Nothing wrong with that.
If anyone's wondering, I'm contemplating doing Earth 2's Superman as my main go-to character. I think the idea of a Superman who isn't Clark Kent in origin a pretty interesting choice to explore.
A Comprehensive Guide to the Multiverse