Niantic revealed last week a Pokemon Buddy system to it’s game saying it will be released in the near future. It was very near since the update has started rolling out over the weekend.
The buddy system is designed as a way to have players gather candy for their pokemon without having to capture them again. Choosing a buddy Pokemon will earn candies simply by walking. The common and mid grade Pokemon will take walking 1KM-2KM before getting candy and the rare Pokemon are 3KM. Datamining has revealed that legendary creatures such as Mew, Mewtwo, Articuno, Moltres, and Zapdos will all be assigned a 3 KM distance.