Gorochu was the name of a scrapped third evolution planned for Raichu during Pikachu’s early development.
Pikachu was originally designed as part of an evolutionary line that included Raichu and a further stage called Gorochu. According to development accounts, the unused Pokémon was imagined with prominent fangs and horns, giving it a more intimidating appearance than Pikachu’s familiar cute design.
Gorochu never appeared in the released Pokémon games. Development constraints, including limited cartridge space, contributed to the removal of the extra evolution. The final Generation I line therefore stopped at Raichu, which evolves from Pikachu when exposed to a Thunder Stone.
Pichu is not the same concept. Pichu was added later in Pokémon Gold and Silver as Pikachu’s pre-evolution, completing the three-stage line in the opposite direction. Gorochu remains an example of an early unused idea that became known through interviews and development history rather than gameplay.