I know this is all wild and very vague and raises a lot of questions. It’s the best explanation I can come up. I really don’t think there’s any way to resolve this without an explanation that’s highly mystical, because it touches on the question of where stories come from.
I like the meme idea, though how does one determine a story’s potency, and who is doing the determining? I suppose that, following up on the meme concept, it could be simply be a story’s “contagiousness.” But if there are multiple versions of each story, don’t we get into the possibility of multiple versions of each character, and a kind of multiplication of parallel universes at points of bifurcation?