Ash received Pikachu as his first partner in the Pokémon anime.
In the opening episode, Ash arrives late at Professor Oak’s laboratory and finds that the three standard starter Pokémon have already been taken. Oak gives him Pikachu, an Electric-type Pokémon that initially behaves defiantly and refuses to remain inside its Poké Ball.
Their bond develops during an attack by a flock of Spearow. Ash protects Pikachu, and Pikachu responds by using its electrical power to defend Ash. That moment establishes the friendship that anchors Ash’s journey throughout the anime.
Pikachu was not the player’s standard starter in the original Pokémon Red and Green games, where the choices were Bulbasaur, Charmander, and Squirtle. Pikachu became the player’s starter in the later Pokémon Yellow game, which was influenced by the anime.