I found the time to work on another Alola form recently, so here's my design for Alolan Chansey (not sure if I'll do Blissey yet though & I'm not planning on giving one to Happiny).
Chansey in the Alola region are known for their incredible strength and their bulky exteriors. Their natural habitat in Alola are in the rugged mountain areas, so they had to learn to fend for themselves when predators such as Lycanroc would try to take their eggs and hurt their offspring. Because of this, they took on this newer form.
Alolan Chansey are almost rarer to find than their counterparts in other regions. They still have their nuturing instincts and tend to any people and pokémon in need, but they will act suspicious at first and will immediately attack anyone it thinks is a predator. Before the Island Challenge was established, it was a rite of passage in the Alola region to seek an Alolan Chansey, befriend it, and receive its egg to bring back home.