Yep. Any pokemon as long as its in the first stage.
First stage is like Charmander, or Pichu. It can also be things like Emolga, Absol, etc. You can pick anything you want as long as it isn't something like Garchomp, or Hydreigon.
Hi! I'm almost done with my SU for your RP. I just have one question about the Alternate Pokemon Form. What do you mean by that? Can it be any pokemon? Thanks for getting back to me.