In the image, many ghost Pokémon are seen, including several Generation III creatures like Sableye, Dusclops, and Banette.
Adding more credence to their arrival in a Halloween event, a leaked image found by data miners points to Generation III as a holiday treat.
With 2017 rapidly coming to a close, Pokémon Go trainers have been riding a rollercoaster of theories about when the next generation of Pokémon would be arriving.
There have been many leaks and teases suggestion Generation III, originally seen in the mainline games Ruby and Sapphire, will be unleashed before the year ends.