Pikachu is the mascot shown on the cover of Pokémon Yellow.
Pokémon Yellow: Special Pikachu Edition was released in Japan in 1998 and later internationally. It is an enhanced version of the first-generation games, designed to reflect elements of the Pokémon anime. Unlike Red and Green, the player begins with Pikachu, which follows the protagonist outside its Poké Ball.
Pikachu’s refusal to evolve with a Thunder Stone mirrors a recurring anime detail and gives the game a distinctive relationship between player and partner. The three traditional starter Pokémon—Bulbasaur, Charmander, and Squirtle—can also be obtained during the adventure, making Yellow different from the original version-exclusive setup.
Pikachu became Pokémon’s most recognizable mascot because of its central role beside Ash in the animated series and its prominent use in games, merchandise, and promotional art. The cover question is therefore about Pokémon Yellow specifically; other first-generation covers feature Charizard, Blastoise, or Venusaur instead.