How about Squirtle Ho-oh, and Lucario?

Squitle do to the fact not only it a fist gen pokemon, kevin has an Avatar of one, that and it is a lot more useful in Brawl then ether Ivysaur or Charizard...

Ho_oh because not only for the phoenix reference, and a partial throwback to the old Mewtwo/Lugia/Ho-oh logo, but it's by far one of the more known second gen pokemon besides it being a legendary under lines the fact that TPM iself is some what of a legendary pokemon fansite.

Lucario he replaced Mewtwo in Brawl, is easily one of the most popular Pokemon, and People thought he was a legendary, but of course there is a legend about Lucario..that and he was most likely based off of Anubis since he looks like a jackle waling on two legs.

~Charles Legend