The plot and gameplay of Pokémon Yellow is largely the same as in Red and Blue, though it features changes to make the game more similar to the animated series. Like Ash Ketchum in the anime, the main character of the game receives Pikachu as their starter Pokémon. One of Pikachu's unique features is that, unlike other Pokémon the player encounters in the game, Pikachu walks behind the trainer and will display emotion. Pikachu will react when the player enters certain buildings and rooms. If the player faces Pikachu and talks to it, a box will appear showing Pikachu’s face and current mood, ranging from murderous to curious to bursting with love. Other minor gameplay changes include a different selection of Pokémon available to catch, all three Red and Blue starter Pokémon being available from NPCs, and the anime characters Jessie, James, and Meowth making appearances.

(Wikipedia)

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