Rotom is definitely an unusual Pokémon. Rumored to be a "Pokémon that has fused with a toy robot," according to Professor Rowan, Rotom has a rather unique ability: it can change shape after interacting with everyday appliances. Here's how to change Rotom's form into Pokémon Brilliant Diamond and Brilliant Pearl.
First, you'll need to get Rotom from the Old Chateau, which requires you to beat the game and get the National Pokédex early. Capturing Rotom will also give you the secret key, which you will need to get the other forms of the Pokémon. After securing Rotom and the key, head to the Team Galaxy building in the northwest corner of Eevopolis. Upon entering you should notice a slightly discolored portion of the wall to the left of some bookshelves. Interact with it and a secret room will open. Inside there will be many appliances that Rotom will be able to own. Interaction with each fixture will give Rotom a different shape, which we have listed below:
- Light bulb: the basic form of Rotom, electric / ghost type.
- Microwave oven: Heat Rotom, electric / fire type.
- Washing Machine: Wash Rotom, Electric / Water type.
- Refrigerator: Frost Rotom, an electric / ice type
- Electric fan: Fan Rotom, Electric / Flying-type
- Lawnmower: Mow Rotom, electric / for grass
Rotom will change shape when you interact with one of these appliances in the Team Galaxy building, but you can also change shape using the Rotom Catalog located in your key items, which you will get when you discover its new shapes in the secret Camera.