Niantic just revealed that Ditto is now in Pokémon GO.
Ditto shape shifts and mimics other Pokémon in looks and traits. It only reveals itself when caught. Ditto will be useful in Gym battles by copying the look, type, and moves of the first Pokémon seen.
More information about Pokémon GO and the updates are available on this website including how the Nearby feature has been tweaked.
Pokémon GO is available on iOS and Android devices.