What is what animal is pikachu?

Pikachu's species is never explicitly stated in the Pokémon universe, but it's generally classified as a Mouse Pokémon. While it has some characteristics of rodents like its small size, long tail, and twitching nose, it also possesses unique features not found in real-world mice, such as its electricity-based abilities and distinctive cheek pouches. It's essentially a fictional creature inspired by rodents but with fantastical additions.