Which Pokémon game first made Pikachu the player’s required starting partner?

Pokémon Yellow first made Pikachu the player’s required starting partner.

Released in Japan in 1998, Pokémon Yellow is an enhanced version of the first-generation Game Boy games. It was designed to reflect elements of the animated series, so the player begins with Pikachu rather than choosing Bulbasaur, Charmander, or Squirtle.

Pikachu follows the player outside its Poké Ball and reacts to the player’s actions. The game also includes Team Rocket characters Jessie and James, who were associated with the anime. Unlike the original Red, Green, and Blue games, Yellow gives the player opportunities to obtain all three traditional starter Pokémon during the adventure.

Pikachu is not simply a selectable option in Yellow’s opening sequence: it is the required partner. That distinction separates Yellow from later games that offer Pikachu as one choice among several starting Pokémon.