When Niantics release the Pokemon Go game for the first time, the first thing that many people notice was that one first gen Pokemon was missing from game. Ditto. It was later discovered that the code for Ditto was in the game but the Pokemon was not released until now.
Because of the power of Ditto, we understand Niantics might have needed more time with the Pokemon and now they are ready to release it into the wild but catching it might not be so easy of you are picky Pokemon trainer.
Instead of appearing as Ditto on the map, the elusive Pokemon will appear as some of the most common Pokemon like Zubat, Rattata and Pidgey and it will only reveal itself once you’ve caught it.
That means you will have to catch all the Pidgey, Zubat and Rattata you come across from now on.