Jirachi

Jirachi is a dual-type Steel/Psychic Mythical Pokémon that was introduced in Generation III of the  games. In Super Smash Flash 2, Jirachi appears as one of the Pokémon that can be released from a Poké Ball or Master Ball to aid the player.

Pokémon description
Jirachi is a small, white, humanoid Pokémon. It has short, stubby legs and comparatively longer arms. There are flaps on the underside of its arms, which give the impression of long sleeves. On its belly is a curved seam, which conceals a third eye, known as its "true" eye. Additionally, it has a normal pair of circular eyes on its face, with small, blue triangular markings underneath. On its head is a large, yellow structure with three points extending outward: one from the top and one on either side. On each point is a blue tag, known as a "wish tag". A rounded extension hangs from either side of the yellow structure, framing Jirachi's face. Two yellow streamers flow from this Pokémon’s back, resembling comet tails. Jirachi hibernates for extensive periods, forming a protective crystalline shell as it sleeps. However, it is still capable of fighting while asleep if it is in danger. It awakens for seven days every thousand years, but can also awaken if sung to by a voice of purity. During the short periods when it is awake, Jirachi is said to grant wishes. However, in the anime, Jirachi cannot create an object that is desired from a wish. Instead, it teleports the desired object to the person that made the wish. In the Pokémon Adventures manga, Jirachi's wishes are granted by writing on the three tags located on its head. Due to only having three tags, Jirachi can only grant three wishes. The anime further reveals that Jirachi's awakening is linked to the Millennium Comet, and that its third eye has the ability to absorb the energy Jirachi needs for hibernation. Although it is extremely rare, Jirachi can be found in the mountains. Jirachi is the only known Pokémon capable of learning the move Doom Desire.

In Super Smash Flash 2
As stated above, Jirachi can be released from a Poké Ball or Master Ball in Super Smash Flash 2. Jirachi is one of the rarest Pokémon to find in a Poké Ball, which is likely due to the fact that it is a Mythical Pokémon. Despite its rare appearance, it will simply use Fly in the air for a few moments when summoned before flying off. It has no effect on the player characters and is little more than a novelty. However, for the first time Jirachi appears, the player will unlock the Sky Pillar stage.