Alright, here's something i thought about, an explanation for the reason why Pokemon and Furries can exist in Paul Universe.

Pokemon are just Furries, but they have a gene, that changes their appearance and gives them bizzare biological quirks, i call that gene, PKNA.

While Fishmen and a Furry (like a Cat) can't get any off spring, cause their genes don't mix in too well (tho the chance of that happening is rarer than winning a lottery), PKNA can make it that no matter with which Pokemon you copulate with, there almost always will be a result.

Like, lets take a Fishmen and a Sylveon, the resulted off spring would be either Pokemon Fishmen, Vaporeon or Regular Fishmen.

Id say, getting a normal animal offspring and pokemon offspring is around 25 to 25, while the other 1% can result in a special baby, which is pretty much Ditto, or other chances may result in a baby that's shiny, has gigantism or microsm or both, they aren't common, but they aren't as rare as a Baby Ditto.

In short, for those who don't wanna read it: Pokemon are just furries, but have different appearence and strange biological quirks, simple.