With the upcoming release of Pokemon Scarlet and Violet, Game Freak's creature-collecting RPG franchise may officially cross the threshold of 1,000 monsters logged in the National Pokedex. Even so, many of Pokemon's best-known creatures are from the original 151 line-up that debuted with 1996's Pokemon Red and Green in Japan. They were propped up by the phenomenon of Generation 1 games, the ongoing anime adaptation, and its popular trading card game, but over the years Game Freak has also given the first 151 extra attention in various forms.
Charizard, the final evolution of Kanto's Fire-type starter, is perhaps the best example of special treatment outside Pokemon's mascot Pikachu. New battle gimmicks often include Charizard, with it getting two Mega Evolutions in X and Y, as well as a Gigantamax form used by Champion Leon in Sword and Shield. The idea of regional variants introduced with Sun and Moon was also exclusive to Kanto region monsters appearing in Alola. Yet few Gen 1 Pokemon have received as much attention as Eevee, whose cute design and expanding roster of evolutions make it nearly as recognizable an icon for the brand as Pikachu. Despite its prominence, there are still a number of types that have yet to receive so-called "Eeveelutions."
Eevee's Growth Throughout the Pokemon Franchise
A few Pokemon in the original Kanto games could only be received through special means, such as trading a Spearow or Pidgey to get Farfetch'd. Eevee was one such giveaway Pokemon, with players only able to obtain a single Eevee from someone at the top of an apartment complex in Celadon City. This rarity only fed into the Normal-type's appeal, which was based around giving users the choice for which of its three evolutions they preferred.
Eevee's Pokedex entry in Red and Blue says "Its genetic code is irregular. It may mutate if it is exposed to radiation from Evolution stones." A Water Stone will evolve it into the Water-type Vaporeon, a Thunder Stone into the Electric-type Jolteon, and a Fire Stone into the Fire-type Flareon. This gimmick would be expanded to various environmental factors. Generation 2 introduced the Psychic-type Espeon and Dark-type Umbreon (one of the few representatives of the new typing), both of which evolve with high enough friendship during day or nighttime, respectively. Generation 4 introduced the Grass-type Leafeon and Ice-type Glaceon, which require trainers to be near the Moss or Ice Rock in Sinnoh. Finally, Generation 6 introduced the Fairy-type Sylveon as a representative of its new typing that evolved using the interactive Pokemon Amie system.
Evolution requirements for Eeveelutions such as Sylveon would change as systems like Pokemon Amie were phased out, but the whole family remained a popular source of merchandise for The Pokemon Company. Eevee would also become more prominent in spin-off games thanks to its versatility. Pokemon XD: Gale of Darkness and Pokemon Conquest both have protagonists using Eevee, and Pokemon Colosseum starts off with Espeon and Umbreon. Most recently, the Generation 1 remakes Pokemon Let's Go, Pikachu! and Eevee! position the Normal-type monster as a starter akin to Charmander, Squirtle, and Bulbasaur; one with unique attacks based on various types.
Pokemon Types Without Eeveelutions
On top of new evolutions, Eevee has benefited from the range of battle gimmicks introduced throughout modern Pokemon games. In Sun and Moon it got the exclusive Z-Move Extreme Evoboost, which raises all its stats (a technique referenced by Leaf and Eevee's Sync Move in Pokemon Masters EX). Pokemon Sword and Shield also gave Eevee a Gigantamax form with the attack G-Max Cuddle, which makes Pokemon of the opposite gender infatuated. Yet, Generation 8 broke the pattern of new Eeveelutions being added every even number, which means there are still nine types unrepresented in the Eevee family:
One could also make the argument for a pure Normal-type evolution, bringing the number up to 10 unrepresented types. Over the years, many fans have sketched up their own Eevee evolutions based on types like Ground, but after Game Freak skipped over Generation 8 it's unclear whether the developer has any intent to finish the set. Pokemon Scarlet and Violet offer another opportunity, whether it introduces a new type for Eevee to embody or back-fills new evolutions similar to Espeon, Glaceon, and Leafeon. With Eevee's continual attention as a sort of mascot for the Pokemon brand, anything is possible.