Lucario

Lucario is a playable character in Super Smash Bros. Brawl, entering from the Pokémon series 4th Generation of games. He was confirmed through a Sticker screenshot which showed Lucario's icon at the bottom, but it wasn't officially confirmed until later, when Nintendo started leaking game videos on the game just days before Brawl's Japanese release. It is unknown what Lucario's moveset is, neither is it known what his statistics are, but it is known he'll play a part in the Subspace Emissary, in which he will assist Snake at some point in the game. He also appears to fight Meta Knight and the Ice Climbers at one point in the story. Afterwards, Lucario and Meta Knight team up. They later board the Halberd, and team up with Solid Snake.

Lucario appears to have replaced Mewtwo, another Super Smash Bros. fighter from the Pokémon series who was only playable in Super Smash Bros. Melee.

Lucario has a special property no one else in Brawl has - the more damaged Lucario is, the more damage and knockback all his attacks do. It seems to max out at 200% damage. A move that normally did 15% damage did 26% damage when he was at 200%, and knocked the opponent back about twice as far as normal.

Recently, two gameplay videos have been found. They can be found here and here.