User blog comment:AlexSmasher/Mewtwo just proved something/@comment-4115159-20141025171143/@comment-6604133-20141025215511

I'd say the only "other appearances" that don't matter are trophies, since Mewtwo is playable. But stage bosses, assist trophies, and Pokeballs are already being represented as fighters, just not playable ones. Trophies are simply still models on bases.