Pikachu became the Pokémon franchise's main mascot and Ash's longtime anime partner.
Pikachu is an Electric-type Pokémon introduced in the first-generation games. In the original anime, Ash Ketchum receives Pikachu from Professor Oak after arriving late to choose a conventional starter. Their friendship becomes the emotional center of the series and made Pikachu recognizable far beyond video-game audiences.
Pikachu's design was created by Atsuko Nishida and finalized by Ken Sugimori. The character's bright yellow color, pointed ears, red cheek patches, and distinctive tail helped make it especially effective as a logo, toy, card illustration, and animated character.
Pikachu is not the first National Pokédex entry and is not the only Pokémon to appear as a partner character. Its mascot status comes from its central role in the anime, promotional artwork, games, merchandise, and the wider public identity of Pokémon.