Which Pokémon species was created by Atsuko Nishida?

Pikachu was created by Pokémon designer Atsuko Nishida.

Nishida designed Pikachu at the request of lead designer Ken Sugimori during development of the original Pokémon games. Sugimori finalized the design and produced the artwork used for the finished game and promotional material.

Pikachu was introduced in Pokémon Red and Blue and became the franchise mascot after the animated series made it Ash Ketchum's partner. Its yellow body, pointed ears, red cheek sacs, and lightning-bolt tail made it especially recognizable across games, cards, toys, and television.

Pikachu is classified as an Electric-type Pokémon and is described as a mouse Pokémon. A common mix-up is crediting the anime with creating Pikachu; the species existed first in the video games. The anime then transformed Pikachu from one member of the original roster into the best-known symbol of the entire franchise.