Today I learned the ranking of kings (a moderately popular anime) was a real life thing codified by the papacy (the gods in the anime) to keep kingdoms squabbling and in line.

It shaped a lot of European history!
https://en.wikipedia.org/wiki/Precedence_among_European_monarchies

Precedence among European monarchies - Wikipedia

@makahi The article itself does state that this was a prevalent problem among European monarchies and especially the HRE and the King of France. So it's more that it was formalized as a list by a pope at one point rather than a whole-sale invention by them.
@KatBuchM that's a good point, I'll update my wording from "invented" to "codified"