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Rotom has a body of plasma and is shaped like a lightning rod. There is a whitish blue aura of electricity around it that forms lightning bolt-shaped appendages. It has teeth, and its unique, blue eyes have a dividing line across them. As seen in the anime, Rotom will often pull pranks on unsuspecting people. Also seen in the anime, Rotom has the ability to time travel.
Rotom has the ability to enter and control appliances. Starting in Platinum, it also has five extra forms, each based on a household appliance, which can be accessed by possessing specific appliances. The possessed appliances are based on a microwave oven (Heat Rotom), washing machine (Wash Rotom), refrigerator (Frost Rotom), electric fan (Fan Rotom), and a lawnmower (Mow Rotom). When Rotom changes form, its eyes and electric aura change colors and its aura appendages take on different shapes: red with oven mitts as Heat Rotom, blue with clothespins as Wash Rotom, purple with lightning bolts as Frost Rotom, yellow with air curls as Fan Rotom, and green with a ripped strip as Mow Rotom.