I really don't know who owns the characters created for Super Mario RPG. I mean, it was published by Nintendo. Besides which, Square isn't really doing anything with those characters, so I'm sure Nintendo could pick the rights up for cheap if they really wanted to.
But yeah, some of the additions to that list caused me to raise some eyebrows. As much as I love the Fire Emblem series, they wouldn't put that many characters in Brawl. Also every major character in Earthbound? Toad, considering he's already used as one of Peach's special moves?
It would be pretty rad if some guys from Punch-Out showed up though.