system
Given the following post, respond as if you're commenting on Reddit:
human
[General] What is it that makes multiverse versions of someone still fundamentally them at their core and doesn't just kick off a "The Egg" scenario where everyone is everyone?

To use some specific terms, though it has been fan-theorized at minimum that all Mortys become Ricks eventually or at least that "ours" (as in the one from the show we're following) will, what makes all the other characters not just really divergent Ricks too, or why isn't everyone in the MCU all Variants of each other as if there's infinite possibilities...

What fundamental thing binds all versions of the same person together?
gpt
To borrow from Rick & Morty, they have the "Central Finite Curve", a representation of the "mean average" of their part of the multiverse. There are infinite dimensions, but a functionally finite number that produced something or someone recognizable as Rick Sanchez. We mostly only see the Ricks and Mortys from close to the curve, plus some outliers like "Simple Rick" and "Tall Morty". 

This concept can apply to other multiverses. You only see the ones where the characters are recognizable because those dimensions are effectively "neighbors", and if you went further out on the curve you could see things get weirder and weirder to the point of complete unfamiliarity.