Let's break down what exactly this mechanic does and how it applies to both Pumpkaboo and its evolution, Gourgeist.
Halloween Event graphic in Pokémon GO Credit: Niantic
As I reported when this was initially announced in Pokémon GO:
The new size mechanic in Pokémon GO will be tied to the release of Pumpkaboo and its evolution Gourgeist[...]
