When you bring Ash's Pikachu to the Valley of Pikachu, you can get the hat from that Pikachu to wear on your character.

Maxie is UltraSun exclusive and Archie is UltraMoon exclusive

Lysandre looks like a zombie

DLC for the Battle Tree where you can download various opponents from either previous games or from the cartoon.

New Pokémon for next years movie event. Normal/Ghost. Looks like a lamb.

Uhmmm don't tell ><