As usual, Niantic have not announced all the bonuses for the event beforehand.
We now have English names for old and new Pokémon and characters, and Rainbow Muk abound! Check the trailers and additional information here.
We now also have Silvadi, the evolution of Type Null, and Jangmo-o’s evolutions. Furthermore, the Sun and Moon anime starts with a special on November 17th in Japan.