Only in Ultra Sun & Ultra Moon
SOS Encounter: Poni Plains (15%)
Its base catch rate is 30 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Love Ball or Premier Ball.
Evolution: Happiny → Chansey → Blissey.
Blissey in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)