Ash Ketchum was given Pikachu at the start of the Pokémon animated series.
In the first episode, Professor Oak assigns Ash a Pikachu because Ash arrives late and the three traditional starter Pokémon are already gone. Pikachu is reluctant to enter its Poké Ball and initially resists Ash’s commands, creating an important early conflict.
Their relationship changes when Pikachu protects Ash from attacking Spearow. The event establishes Pikachu as Ash’s companion rather than simply another team member, and the pair remain closely associated throughout the anime’s early decades.
Bulbasaur, Charmander, and Squirtle were the original video game starter choices, but none was Ash’s first assigned partner in the television series. Pikachu’s role also helped make it the franchise’s best-known mascot as Pokémon approaches its 30th anniversary.