Pichu is an Electric-type Pokémon introduced in Generation II. It is also known as the 'Tiny Mouse Pokémon'.
How to Obtain
Pichu can be obtained in two particular patches of grass in Mysterious Grotto, one of which is adjacent to the Battle Tower. It is a 100% chance to encounter Pichu in them (Without a Lunatone or Solrock in the Deoxys area). It can also be obtained from trade and the Pokémon Roulette.