Generation 2 and Baby Pokemon
The official announcement:

Trainers, Professor Willow has discovered Togepi and Pichu hatching from Eggs! Starting later today, Trainers will have the opportunity to hatch these and several other Pokémon that were originally discovered in the Johto Region in Pokémon Gold and Pokémon Silver video games. These are the first of more Pokémon coming to Pokémon GO over the next few months. Be sure to use the hashtag #PokemonGO on Twitter to share your experiences as you explore your local neighborhoods with family and friends, walk to hatch these Pokémon from Eggs, and register them to your collection this holiday season. We can’t wait to see what Pokémon you’ve hatched!

We also have another special treat for you. Starting later today through December 29, 2016, 10:00 A.M. PST, you’ll find limited edition Pikachu all over the world. These Pikachu will be wearing a festive hat to celebrate the season! Use the Pokémon GO AR camera when you encounter them in the wild to take their picture and share it with us using #HolidayPikachu. —The Pokémon GO team

Gen 2 Hatch Table

PokemonEgg DistanceBuddy DistanceCandy
Igglybuff2 KM1 KM25
Cleffa2 KM1 KM25
Pichu5 KM1 KM25
Togepi5 KM5 KM50
Magby10 KM5 KM25
Elekid10 KM5 KM25
Smoochum10 KM5 KM25

Pikachu gets a Santa hat!

Hat remains after evolving into a Raichu. Santa hat Pikahu will appear on your nearby tracker.

And a new welcome screen...

New Welcome Screen