Kinvara

(This is not to be taken seriously in case you're wondering.)

Bulbasaur, Ivysaur, Venosaur: A frog-lizard-thing with a plant on its back. Fair enough.

Charmander, Charmeleon, Charizard: Ok. So we got lizard-> bigger lizard -> dragon. Where'd the wings come from?

Squirtle, Wartortle, Blastoise: Why does Wartortle have such a goofy tail? It turns into a regular tail when it evolves so what's the point? And how does Blastoise have metal water ...