Professor Oak, Samson Oak
The first games in the Pokémon franchise started with a friendly visit to Professor Oak. He gave the character their first Pokémon because he wanted them to help him fill the Pokedex. Pokémon Sun and Pokémon Moon include a Professor Oak too.
This Professor Oak isn’t the one that you’re familiar with. That one is still in Kanto. Instead, Alola has its own researcher named Oak. Samson Oak focuses on one of the world’s new discoveries: regional variant Pokémon. Those are the creatures that have multiple forms depending on where they originated from. It’s a new mechanic for these two new games.