Which Pokémon species became the franchise's mascot?

Pikachu became the Pokémon franchise's mascot.

Pikachu is an Electric-type Pokémon first introduced in Pokémon Red and Blue. Its yellow color, rounded shape, expressive face and lightning-bolt tail made it especially recognizable. The character was designed by Atsuko Nishida, with the final design completed by Ken Sugimori.

Pikachu became even more prominent when it was chosen as Ash Ketchum's partner in the animated series. The anime helped establish Pikachu as the face of Pokémon for audiences who had never played the games. Its voice in the Japanese anime has primarily been performed by Ikue Ōtani.

Pikachu was not the only candidate considered for a leading promotional role. Clefairy was also considered, and the three original starter Pokémon were familiar from the games. Pikachu's broad appeal, distinctive silhouette and pet-like design ultimately made it the safest mascot for merchandise, television and international promotion.