Being the main character of one is not a breif appearance, it's main character status. Being the mascot of the freaking famicom, Nintendo's most notable system is not a breif appearance. And what game was ROB the
main character of? And why would he not work as a playable character? Because he's flat? Nope, in Janken Disk Jo he can move just as well as Kirby can. Like Paper Mario he can remain flat while changing perspective.
This sprite sheet proves it:
So let's discuss other problems with Diskun. Is being Japan only a problem? Nope! Not to mention gamers from Japan should recognize him. Is being irrelevant a problem? Of course not, Pit wasn't during Brawl and characters retro characters aren't suppose to be relevant. Is moves a problem? Don't count on it. Diskun can copy any move from any Famicom game and also use many things from Janken Disk Jo.
Hotfeet444 I believe, but if you read the comment above this, you'll see Diskun is perfectly feasible and deserving. I think you will find that it's
Super Effective!
Yeah, I'm suggesting/predicting a character that isn't Little Mac or Ridley. Sue me.