>>332182452005 was the best design with Kath Soucie. I've got a bunch of those episodes I recorded onto a DVD.
Also, if you want to look at pokemon from a game POV, the game simply comes down to stats. You could play the game without even seeing the pokemon. If all you saw was a number and form to indicate what it is then you can remember its stats, type, and moves etc. So making a new form that isn't just aesthetic is essentially making a new pokemon, even if it's just a new form. You could replace every pokemon in this game to look like Pikachu, but they'd all be different, and the game would still play the same. It'd just be dull to look at 800 Pikachus. So from a design perspective, as
>>33218237said, it's easier to just change the gameplay rather than come up with new designs.