The Elusive Pikachu: Only Three Pokémon Available in All Games.

Only three Pokémon, Magikarp, Psyduck, and Magnemite, are catchable in at least one of every mainline pair of Pokémon games, while Pikachu is not. The reason for Pikachu's absence in some games is due to the controversy surrounding the release of Black and White, which only featured brand-new Pokémon. Magikarp is obtainable through a salesman on Marvelous Bridge in Black and White, while Psyduck and its evolution Golduck are available in Unova. Magnemite can be found in White Forest in White-exclusive locations.