Rotom

RGeneration IV. It is known as the 'Plasma Pokémon'. It is one of the top five rarest Pokémon in the game.

rotom was a dick :^)
Rotom used to be in the 2015 event in which you could find it if you had a -type Pokémon and an -type Pokémon in your party and searched at Mt. Cinnabar. Now, it is only obtainable through trading because it got removed from the Pokémon Roulette.

Forms
Rotom can be transformed by interacting with any of the items listed below. These items are present in a Brown, Wooden house in Elegant Valley where you can also check your Pokemon's EVs and IVs. The 6 forms are:

Moves when caught

 * No data

Moves that can be taught by Move Re-learner

 * No Data

Moves that can be taught by TM's

 * No Data