I understand. It took me quite a while to get used to it myself. According to Louie there's a few that have gone through drastic transformations, though the majority here seem to come from their own worlds where this is the default appearance.

[As he's talking he's leading her to one of the double doors at the back of the large library space that makes up the academy's entrance. That leads to the track field, an expansive study-and-work area. Specifically he walks with her to one side where there's a small set up of seating by a couple of trees.]

So! Let me introduce my Pokemon to you. We'll start with Snow, the second partner I acquired. [And out of the Pokeball comes a Quaxwell, who almost immediately starts brushing off his feathers and getting all Sorted Out.] His species is Quaxwell, and he is a middle stage Pokemon.

Some, though not all, have "evolutions," which similar to the conventional idea but on a much quicker time table. That's one of the similarities I was discussing earlier- even Pokemon vastly different from each other in every way will share the fact that they can evolve in new forms.

Snow in particular- [Who looks up at his name, posing after a moment.] -is a two stage Pokemon. He started as a much smaller duck species known as Quaxly, and has one more stage to go before he is considered "fully evolved."

Your own Espurr, if I remember correctly, will have a single stage evolution, but not without its own particularities. Espurr is a Pokemon whose final form will depend on what biological gender they are.