@alyx @crunklord420 Bill manages to transform himself into a Pokemon in Red/Blue so I'd assume that even if it's not possible normally, it would be possible if they transformed themselves. I'd assume humans would need a specialized type of ball, like how only Beast Balls work on Ultra Beasts; the backstory behind Beast Balls implies that pokeballs can work on things that aren't pokemon, they're just extremely ineffective on them.