For those still playing, there's a Halloween special going on. Ghost type pokemons are everywhere. It's like someone hacked poke radar, but that someone is Niantics.
Also, the buddy reward distance is cut by 6 or 4 times. So if you are walking a pokemon that gives you a candy after 3KM, now you get one after 0.5KM. So do 5KM and you get 10 candies.
Candy reward from catching a pokemon is also doubled.