Right off the bat on this community day thing, I caught Shinx and Roselia, over the course of the day I caught three shiny Machops, another Roselia, two Swablu and a Gible.
Also I never noticed there was a prelude to SuMo in gen VI. In XY you can meet a backpacker in a hotel and he'll give you a 'strange souvenir' from a unknown region, these are later shown to be from Royal Avenue in SuMo. In ORAS, when you reach Hoenn's Battle Resort you find a character called Looker who's been in the games since gen IV, he has amnesia and only knows his name, he also holds a Audinite and that's it he just sits on a bed in a hut for the rest of the game.
In SuMo during the UB missions, you're working with him and Anabel, he mentions that Anabel was found washed up on Poni Grove's beach about ten years before the games events, she only remembered her name and had vague recollections about defending a tower, it was implied she came from gen 3 RSE games where she was a trainer in the Battle Tower and that world may have been destroyed by the Ultra Beasts and she fell through the ultra wormholes, I wonder if they'll expand on that in the future.