Pichu

Pichu is a Pokémon introduced in the games Pokémon Gold, Silver and Crystal. It is the pre-evolved form of Pikachu, the Pokémon mascot. The Pichu that appeared in Super Smash Bros. Melee is male, like his evolved counterpart, Pikachu.

Super Smash Bros. Melee
Pichu was a playable fighter in Super Smash Bros. Melee. He was an unlockable character, unlocked by beating Event Match 37: Legendary Pokémon. After beating it, Pichu will appear to challenge the player and, if defeated, will become a playable fighter.

Pichu is a clone of Pikachu, meaning he has all of his attacks. Pichu is a less favorable character as he is the lightest and he is easily thrown off the board. Also, all of his electric attacks (including Skull Bash) causes damage to himself. However, due to his small size, and quick nature, he is usually good for fighting larger enemies, whose attacks hit high in the air. Also, he packs more power than Pikachu, namely because the Pichu species in general have a hard time storing their electricity. Therefore, more power is released and they hurt themselves.

As such, Pichu will usually cause a lot of losses to the player when they first play as him, but with practice, he can become a dangerous mouse. Additionally, Pichu has two taunts, one for each direction he's facing. In the game, Pichu was voiced by Satomi Koorogi in both English and Japanese, who does his voice in the Pokémon Anime.

Classic
''A baby Electric-type Pokémon identifiable by its big ears. Pichu evolves into Pikachu. It's not very skilled at storing up electrical energy and will sometimes discharge it if jarred. Although it's small, it has enough electrical power to give even an adult quite a shock. It's often startled by its own power.''

Adventure
''Compared with Pikachu, Pichu is a tad more nimble and a little more difficult to hit. Those are the only two advantages, however, and since Pichu damages itself when it uses electrical attacks, it's best suited for handicapped matches. Even though Pichu's tough to catch, it's easy to throw its tiny frame great distances.''

All-Star
''Pichu is the lightest character in Super Smash Bros. Melee., and it's top of the class in weakness, too! For Pichu, it's all about scampering here and there to pick up items that will help it survive. The first warp in Agility causes 1 point of damage to Pichu, and the second causes 3, so try to limit the number of times you use the move.''

Trophy Information from Super Smash Bros. Brawl
''A Tiny Mouse Pokémon. Because its electric cheek pouches are still small, it cannot store electricity yet. Pichu has been known to flaunt its courage by touching tails with others and setting off sparks. It is easier for Pichu to build up electricity when the humidity is lower. Pichu will evolve into Pikachu.''

Trivia

 * In Super Smash Bros. Brawl, Pikachu can wear Pichu's goggles from  Super Smash Bros. Melee as part of a color change.
 * In the Mario Party DS minigame Hanger Management, an animal passing around bears many resemblances to a Pichu. Maybe it is.