@Wiimeiser
I always assumed it was Terra, (the first character you play as) but that’s debatable as the game doesn’t always focus on her, and at times characters get separated, and get their own side story paths, and such.
I noticed alot of RPGs or Adventure games tend to always change the entire cast, or setting every game. Even Zelda, the RPG Mario games, and the EarthBound series are guilty of that.
That said, I wonder if we’ll ever see Ninten from “EarthBound Beginnings” (formally known as “EarthBound Zero”) in SSB as an echo, or alternative costume for Ness.