TL;DR: Raichu was supposed to evolve into a Pokemon called Gorochu but it was dropped due to balance issues and the line was cucked forever when Pichu and Alololololololololan Raichu were introduced.
Ive been reading a lot of headlines recently about an interview with Atsuko Nishida, a graphic artist who helped design many of the original Pokémon, including series icon Pikachu. The main takeaway is that Pikachu, the famed electric mouse, was not supposed to be based on a mouse at all, but rather a squirrel that Nishida wanted to keep as a pet. I suppose in hindsight the large tail should have made that rather obvious, but Ive accepted the mouse myth my entire life.
What I didnt realize about this interview until today was that it was also revealed that Pikachu was supposed to actually be a three-stage evolution Pokémon. In the game, Pikachu evolves into Raichu with a Thunder Stone, which was a subject of much contention in the animated series, as Ashs Pikachu never wanted to evolve, but there was actually supposed to be one more evolution passed Raichu as well.
The final evolution of Pikachu, Gorochu, actually had fangs and horns according to Nishida, but was eventually cut from the game because of balance, which seems like an odd thought considering that Raichu is usually not thought of as a powerhouse in the game, and it should be easy enough to adjust values to nerf any Pokémon and make them less powerful. There are no third stage electric types in Gen 1, so it seems like Gorochu could have easily fit in there, and other iconic Pokémon from Gen 1, Squirtle, Bulbasaur, Charmander, all had a third and final evolution stage.
Im trying to picture an evolved Raichu with fangs and horns, which is kind of amazing, and at least one artist has made an attempt to draft what Gorochu could have looked like. Fangs and horns are present, but its still rather cute.
But Raichu has never evolved, not in seven generations when many other Pokémon that originally did not have further evolutions have gotten them. The only addition to the Pikachu family has been earlier evolutions like the baby Pichu, or the Alolan version of Raichu, which is not the same thing.
Will Gorochu ever make its way into a game? It seems unlikely now, given that weve gone seven generations without a true Raichu evolution. We should see a new Pokémon game announced this year (for the Switch!), but I would not expect Gorochu to make an appearance after more than 20 years.
Still, its a neat bit of Pokémon history, and its amazing to still learn new things about the series all this time later. Pikachu is a squirrel and could have had a powerful evolution with horns and fangs. This is like when I learned the original draft of Sonic the Hedgehog had him have a guitar, motorcycle and busty girlfriend (seriously, look it up).