None. I would'nt mind seeing Roy again, I feel like their is room for him. As for Mewtwo, as much as I like him, I feel like their is already enough pokémons in the roster (especyaly when it comes to the first 150).
I always thought Pichu was a interesting character with it's risk/reward moveset. But I don't see him making a comeback but I would prefer him over Mewtwo since he is in wave 2.
I would much rather keep Toon Link over Young Link.
As for Dr.Mario. Forget about it, it is clear that ppl are sick of clones, Brawl tried to fix this abit with mixing up clones alot more than in melee. But I don't see them readding a complete clone of a game franchise that we have'nt seen a game for years. I'd like to see Dr.Mario as a costume, but nothing else.
What?! I can't hear you over all this awsome! - Pyrrhon (Kid Icarus:Uprising)
Final Ultimate Legendary Earth Power Super Max Justice Future Miracle Dream Beautiful Galaxy Big Bang Little Bang Sunrise Starlight Infinite Fabulous Totally Final Wonderful Arrow...FIRE! - Wonder-Red (The Wonderful101)
