Pikachu, Pichu, Jigglypuff, and Mewtwo were the playable PokÈmons in Super Smash Bros. Melee. I actually think that Pichu was the weirdest choice to include, as Pikachu is already in the game, so why pick a different evolutionary stage? There were better choices. Jigglypuff actually doesn't seem to out of place for me. Besides, I've used it twice to do the infamous Event Match 51 with no falls using the famed "Jigglypuff strategy."
As I remember hearing, so far, Pikachu is the only confirmed PokÈmon to appear in Brawl.