In Pokémon Pokopia, the player character uses Ditto's Transform ability to imitate a human.
Ditto is the protagonist of Pokopia, but the character does not begin by appearing as an ordinary Ditto. After finding its trainer's old Pokédex, it assumes a human-like form based on that person. This disguise lets Ditto take on the role of a human builder while helping Pokémon rebuild their damaged surroundings.
Transform is one of Ditto's defining abilities in the wider Pokémon series. It allows Ditto to change into the opposing Pokémon, copying its appearance and battle characteristics. Pokopia adapts that concept for a life-simulation setting, allowing Ditto to maintain a human disguise and customize details such as clothing, hair, and skin color.
Copycat and Imposter are related Pokémon terms, but neither is the named ability used for this central transformation. The story's unusual premise depends specifically on Ditto's Transform ability.