Although referred to as an electric mouse, Pikachu's design is actually based on a squirrel. According to former Game Freak designer Atsuko Nishida, she was fond of squirrels at the time of Red & Green's development, so she based Pikachu on squirrels. From its red cheeks used to store electricity based on squirrels storing food in its cheeks, to its lightning bolt-shaped tail more closely resembling a bushy squirrel tail rather than the tail of a mouse.