That didn't take long. Mere days after leaks hinted that Pokémon Go would get more monsters, Niantic and The Pokémon Company have rolled Ditto into the game. The critter is a shape-shifter that won't reveal its true form until you capture it -- in other words, the only reliable way to capture a Ditto is to keep playing until you find one at random. In the Gym, it'll assume the looks and abilities of the first creature it sees and stay that way throughout other battles.
Ditto's arrival may not be shocking, but it's a reflection of the challenge the Pokémon Go team faces: how do they keep you playing now that the initial summer frenzy is over, and colder weather makes it harder to venture outside? While daily bonuses and themed events help, some trainers might not play unless there are more monsters and similar fresh content.