Vui is an Eevee that was experimented by Team Rocket gaining the ability to freely change from Eevee into any of its three evolutions: Vaporeon, Jolteon and Flareon and back.
Vui first appeared in Blame it on Eevee. When Red tried to challenge Erika she stated that wouldn't battle him unless he was able to capture any Pokémon of her choice and sent him to catch an Eevee. Red, with the help of Bill tried to battle him, but for every Pokémon that was sent out Vui would turn into the evolved form that could give the upper hand in terms of type. This ability confused both of them at first, but Bill eventually realized his ability and Red managed to discover a way of keeping Vui from sensing the type of Pokémon sent out by him and thus being able to capture it.
It was later used alongside Red's other Pokémon to battle Team Rocket members, who were pursuing Articuno in the Seafoam Islands. Soon after Red sent him to storage, after restoring Aero in Cinnabar Island. It is later discovered that when Red had sent him to Professor Oak, he had been captured by Team Rocket. Later on, Red had rescued him in The Winged Legends. Red also used Vui to battle Bruno on Cerise Island, taking advantage of his ability to change into his evolutions, which was enhaced since Red had three of the Vermilion Harbor evolutionary stones.
Vui was used on Red's test to become Viridian City's Gym Leader, and defeated the last of the Association's Pokémon, Porygon2. It was his first appearance as an Espeon and was not identified as Vui, but Red expressed that he clearly had much trust in the Pokémon. Red later explained to Sabrina that the Pokémon was, in fact Vui after evolving into Espeon, losing his ability to change into his Fire, Water, and Template:Type2 evolutions.
Moves used
