Which Pokémon follows the player throughout Pokémon Yellow?

Pikachu follows the player throughout Pokémon Yellow.

Pokémon Yellow Version: Special Pikachu Edition was released for the Game Boy in Japan in 1998 and internationally in 1999. It was based on Pokémon Red and Blue but was designed to reflect the television anime more closely.

Instead of choosing one of the three traditional starter Pokémon at the beginning, the player receives Pikachu from Professor Oak. Pikachu remains outside its Poké Ball and follows the player through the overworld, reacting to the player’s actions and showing different moods.

The game also changes several early encounters and gives Jessie, James, and Meowth roles inspired by the anime’s Team Rocket trio. Pikachu’s following behavior is therefore a signature feature of Yellow, not a standard rule of the original Red, Green, and Blue games. Later Pokémon titles reused and expanded the idea of visible partner Pokémon.