SOS Encounter: Route 1 (30%), Mount Hokulani (30%, Only in Ultra Sun & Ultra Moon), Route 4 (15%) + 8 more
NPC Trade: Malie City (Only in Sun & Moon)
Its base catch rate is 130 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, Heal Ball or Dream Ball.
Evolution: Happiny → Chansey → Blissey.
Happiny in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)