Had a silly thought. In fantasy stories where things like magic power can be measured, the entire world always uses the same system.
But what if it didn't? What if, for example, there were a difference between "metric MP" and "imperial MP"? What shenanigans might ensue should someone get the units wrong reading a magic "recipe"?
I don't currently plan on pursuing this idea, but if anyone wants to write or has written this story, I'd love to read it.