Niantic with an update for the Pokemon GO added a new pokemon to the game this time “Ditto”. As you know this pokemon has the ability to mimic other creatures which means you can even “clone” a Snorlax for a short time.
That’s why you will have hard time to catch Ditto. This pokemon appears in other Pokemon’s form in the game so you have to catch a tons of Pidgeys to find it (or Rattatas). But once you get one in the gym you can clone the enemy to make some fun!