Eevee is an "Evolution Pokémon". It is called this because it can evolve into one of several kinds of Pokémon by usage of various methods. It is the starter Pokémon for the main character of Pokémon XD, and the starter Pokémon for the rival in Pokémon Yellow.
In Generation II and Generation III, Eevee has two new evolutions. Both of these evolutions are achieved through Happiness. It can evolve into the Psychic-type Pokémon, Espeon, if, after it reaches the required Happiness value, it gains a level during the day. If it reaches this value, and then levels up during the night, it evolves into the Dark-type Pokémon, Umbreon. In Ruby, Sapphire, and Emerald, it evolves into Espeon between noon and midnight and Umbreon between midnight and noon. In Leafgreen and Firered, you have to trade your Eevee to Ruby/Sapphire/Emerald to get an Espeon or Umbreon. In Pokémon XD, Eevee must be given the Moon Shard to hold and then gain a level to evolve into Umbreon and the Sun Shard coupled with gaining a level to become Espeon.
Eevee is a mammalian creature with brown fur, a bushy tail that has a cream-colored tip, and a furry collar that is also cream-colored. Eevee has black eyes and big ears. Eevee has an irregular genetic code and can sometime evolve in accordance to its environment. Seven evolutions for this Pokémon have been discovered so far. Three of these evolutions can also be the result of Eevee being exposed to either a Fire Stone, Thunder Stone or Water Stone.
Most of Eevee's offensive moves are Normal-type attacks; such as Tackle and Quick Attack, but it can also Bite its opponents and use Shadow Ball. Eevee can also learn supportive moves such as Helping Hand and Wish. Eevee is one of the four Pokémon that learn the Trump Card attack. Some Eevee specimens have the ability Adaptive which makes any Normal-type attack that they use become stronger than when used by any other Normal-type Pokémon whose attack power is the same as Eevee's.
Eevee are quite rare in the wild. They sometimes live near cities and towns. It is possible for Eevee to live almost anywhere, and they may evolve to suit their surroundings.
Eevee first appeared in The Battling Eevee Brothers. A little boy named Mikey was hiding the Evolution Pokémon from his three older brothers because they wanted him to evolve it. However, when Mikey's Eevee single-handedly defeated Team Rocket, Sparky, Rainer and Pyro were able to accept the fact that Mikey wanted to keep his Eevee just the way it is.