First of all, I'd keep all of the old guys (INCLUDING NESS! EARTHBOUND FOREVER!!) and just add some new ones.
Good-
Falco, Geno, Magikarp (heh...), Doomba, Peach, Mallow, WarGreymon, Marrill, CRANKEY KONG, Navy, Hinopio
Bad-
Wario, Waruigi (So I can personaly sock him in the jaw), Chocobo, Giygas (earthbound), Star Wolf, One of the team rocket guys, Bowzer, Wart, Shy Guy, Curly Howard, Moe Howard, Larry Fine
Secret guys
SHIGERU MIYAMOTO!, Deezer, Golden Yoshi, Mr. Pants, Poo (or maybe Jeff), Chunky Kong, Boshi, Master Hand, and Metal Peach, Shemp HOward, Curly Jo, and Joe.
Kweeh! Kweeh!