Dia, Pearl and Platinum encountered Rotom on their first visit to the Old Chateau, where it played tricks on them without them knowing its true identity. Later, Dia and Pearl returned to find it again as it was one of the rare Pokemon Charon schemed to capture. Rotom eventually joined them and lent its powers in the battle against Charon. It stayed with Dia after the battle.
In a response to an appeal from Prof. Kukui, Moon was tasked upon bringing this Rotom from a foreign region to him in Alola since it was too weak to be transferred electronically. It merged with Moon's Pokedex to become the Rotom Pokedex.