https://techcrunch.com/2018/09/25/that-weird-nut-pokemon-that-showed-up-in-pokemon-go-its-official-now/

This past Saturday, something pretty weird happened in Pokémon Go: immediately after the monthly “Community Day” event came to a close, a strange, new, never-before-seen Pokémon showed up. And by “showed up”, I mean it was everywhere. Around the globe, this thing was spawning every few feet. A grey blob with a hex nut for a head, it wasn’t like anything that anyone had seen in-game before.

Weirder yet: no one could actually catch it. If you managed to get it to stay in a Pokéball, it would always turn into something else (in most cases, it turned into a Ditto). Just a few hours later, it was mostly gone.