Rayquaza

Rayquaza is a legendary Pokémon in the Pokémon series. It is known as a sky god in the games and the main Pokémon of Pokémon Emerald. It makes its Mario series debut in the Subspace Emissary story of Super Smash Bros. Brawl. During the events of the story, it appears out of a lake in the jungle when its hears Diddy Kong. It attacks him with what is presumably Dragon Pulse, and snatches him in its hand. Afterwards, Diddy Kong screams for help, with Fox, who was in the damaged Arwing nearby (which Diddy found earlier), jumping out to help him. Rayquaza and Fox then duke it out with Fox being the victor and Diddy Kong being saved. Rayquaza sinks into the lake. As to whether it will be in the game later, or if it will be a boss like Petey Piranha, is currently unknown.