Several key illustrators and designers from the early days of Pokémon recently sat down for an interview with Japanese publication Yomiuri. We previously reported that graphics designer Atsuko Nishida based Pikachu's original design on squirrels, but that's not the only Pikachu knowledge she had to reveal.
Later in the same interview, Nishida and art director Ken Sugimori confirmed the existence of a cancelled evolution for Pikachu and Raichu. The final form for the Electric Mouse family would have been called "Gorochu," and it sounds fairly intimidating!
In the game Pikachu only evolves to Raichu, but I hear that at first there was three stages. Why did it end up being only two stages? (Or one evolution)
Nishida: Yes. It was "Pika(chu)," "Rai(chu)," and "Goro(chu)." The Pokémon known as Gorochu bared fangs and even had a pair of horns.
[Editor's note: "Rai" comes from the Japanese word for thunder and "Goro" comes from "Goro-Goro," the Japanese onomatopoeia for rumbling usually used in the context of thunder.]
Sugimori: There wasn't any problem with its appearances, but it was omitted due to matters surrounding game balance.
Gorochu would have leaned into the "monster" part of the Pocket Monsters name, brandishing fangs and horns. Instead of a stage beyond Raichu, we eventually got Pichu, a stage before Pikachu. Sun and Moon also introduced the alternate Alolan Raichu, but Gorochu is forever lost to time.