Cresselia

Cresselia is one of the types of Pokémon species. It was introduced in the fourth generation of games, though wasn't recorded in the Sinnoh Poké Dex. Rather, it was featured solely in the National Dex. It is a psychic Legendary Pokémon, one of many that were introduced in Pokémon Diamond and Pearl.

Description
Cresselia's body is almost swan like with majestic qualities. Part of her head resembles a crescent moon, thus explaining why the Pokémon is considered a Lunar Pokémon. There are only female Cresselia. While Darkrai, another legendary Pokémon from the fourth generation, can induce nightmares into people, Cresselia rids of them and turns them into dreams one would desire. The name of Cresselia derives from the word crescent.

Super Smash Bros. Brawl
Cresselia doesn't appear inside of a Poké Ball in the Wii game Super Smash Bros. Brawl, but will rather be one of the three different Pokémon that appear (and inflict some sort of events on the stage) on the Spear Pillar stage of the game (Dialga and Palkia, two other Pokémon, also appear here, as do the three Legendary trio Pokémon, though the latter are just cameos and have no effect on the gameplay). Once it appears, it'll use Psycho Cut, attempting to hit the opponents. Cresselia also appears as a trophy.

Trophy Description
A Lunar Pokémon. Cresselia appears on Fullmoon Island and, once discovered, flies around different areas of Sinnoh. Its signature move, Lunar Dance, causes Cresselia to faint but recovers all the HP and cures the status conditions of the next Pokémon its Trainer sends out. Cresselia excels at recovery techniques and is unusual in that it appears only in female form.