It would be cool if this game included a hook like Pokemon's trading and collecting. Let's say, different carts have different costumes that can be unlocked through singleplayer. If you play mutliplayer with someone with a costume that isn't unlocked in yours yet, and you beat them, it becomes unlocked. Or you could do the same thing for special moves. Stuff like that would go a long way to making this game a pokemon-sized success.