I don't really know how you deal with something like Frankenstein's Monster to be honest... Was there an Argivan Doctor Frankenstein? That'd probably have to be the only way you can explain it...
For what it's worth, my attitude is that you treat it like a translation of a foreign word or concept into a language that we can understand.
After all, I'm going to go out on a limb and guess that all the planes in the multiverse don't just conveniently share a set of languages with the countries on Earth where it is profitable to market and sell a particular card game. So, by necessity, you kind of have to accept the fact that what we're seeing and reading is a translated/retold version of what is "really happening" out in the multiverse.
Well, sometimes translators may use a familiar concept in one language to help create a point of reference. Don't assume that
Frankenstein's Monster is literally supposed to be the same one as in the Mary Shelley story. Let's just assume that it's a monster type thing which was created by a mad scientist from reanimated body parts, and that the easiest way to explain what it is to you or me is to simply call it "Frankenstein's Monster," because that's an analog in our language and culture which makes sense to us.
I'm not saying this is the "correct" way to think about these, but it's a way I like to get around Shakespeare in flavor text, Frankenstein in card names, and Einstein in the art for
Presence of the Master without having to assume that those people or things are literally supposed to exist out in the multiverse.