Which Pokémon game first had Pikachu follow the player outside battle?

Pokémon Yellow was the first Pokémon game to have Pikachu follow the player outside battle.

Released in Japan in 1998, Pokémon Yellow is an enhanced version of Pokémon Red and Green. It was designed partly to reflect the Pokémon anime, so the player begins with Pikachu rather than choosing Bulbasaur, Charmander, or Squirtle.

Pikachu follows the player through the overworld and reacts to the player’s actions. The game also incorporates anime-inspired characters and events, including Jessie and James of Team Rocket, giving it a distinct identity compared with the earlier versions.

The following-Pokémon feature later returned in several games, including HeartGold and SoulSilver and the Nintendo Switch titles Let’s Go, Pikachu! and Let’s Go, Eevee! Those later appearances can make the feature seem newer than its original debut in Yellow.