Yoshi's universe... I don't quite see anyone else who would fit (THAT IS NOT AN OBSCURE, UNNECESSARY BOSS WHO WOULD DO NOTHING BUT LOOK COOL). Please do not say Birdo belongs in Brawl. Yoshi might as well be tied in with "Team Mario" and have the Mushroom Emblem and SMB victory music... or perhaps not. It doesn't seem like it'd be quite right... It would makes just as much sense as Bowser sharing Mario's emblem and victory jingle--if you think, the jingle Bowser WANTS to hear is Mario's game over music.
Perhaps, every character should have their own victory tune, regardless of whose "team" their emblem indicates? Peach's would be the short piece heard when you save her in SMB. Ganondorf's would be the music heard when you die in Ocarina of Time, maybe (or perhaps in Twilight Princess... hang on, I don't remember TP's death music....).