The special Rotom character in Pokémon Pokopia is named DJ Rotom.
DJ Rotom is a Pokopia character based on Rotom, the Electric/Ghost Pokémon known for possessing electrical appliances. In the game’s story, this Rotom has possessed a stereo system, giving it a music-centered identity and explaining the “DJ” part of its name.
Rotom was introduced in Generation IV and is unusual because it can inhabit certain machines and change forms. That concept makes it a natural fit for Pokopia, where Pokémon interact with objects, buildings, tools, and restored human technology. DJ Rotom extends the species’ possession theme into a character associated with entertainment and community life.
Rotom Phone and Rotom Pokédex are other well-known machine-related Rotom concepts from the wider Pokémon series, but neither is the named Pokopia character. The answer also is not DJ Pikachu: the game’s special Pikachu is called Peakychu. The key clue is the combination of Rotom’s appliance-possession ability and a stereo system.