What if Pokémon had wild-card variants, like Viva Piñata? They're rare minor differences that don't change the color or anything too major about the design. Maybe you get an extra tail or horns, or a fur pattern can be different, or the shape of a body part can have variations. Like Spiky-Eared Pichu.

Putting aside that they'd literally never do this, do you have any ideas for Pokémon wild-cards?