The Season of Legends began yesterday in Pokémon GO, bringing three months of hemisphere-exclusive spawns to the game along with a change in the Egg pool. All of this, though, we knew was coming. One thing we didn't know was coming, however, was the release of Shiny Arcanine in the wild.
Shiny Arcanine isn't wholly new to Pokémon GO. Previously, one could acquire this Pokémon by catching and evolving a Shiny Growlithe. This isn't isn't the first time we've seen evolved forms Shiny in the wild. Species available to Mega Evolve including the Kanto starters, Beedrill, Abomasnow, Pidgeot, Gengar, Houndoom, and Ampharos can all be encounter Shiny. In addition to this, sometimes Pokémon with baby forms such as Clefairy, Wobbuffet, and Jigglypuff have seen Niantic unlock their Shiny encounters.
Arcanine, though, has neither the ability to Mega Evolve nor a baby form, which had led some to theorize that Niantic has done this for a thematic reason. While it isn't technically a Legendary, its classification is literally "the Legendary Pokémon" in the Dex. The current theory is that Arcanine has gotten a Shiny release specifically to tie-in to the Season of Legends. Pretty cool.
Others theorized that when Niantic said that all Generation One species could be Shiny after Pokémon GO Tour: Kanto, that this means the evolved forms are all also eligible. This is supremely unlikely. Of all the evolved forms out right now, and there are many, the only one currently being reported as having a new ability to spawn Shiny in the wild is Arcanine.
In addition to this sneaky drop, Niantic also confirmed the new Egg pool:
2 km Eggs: Growlithe, Cubone, Magikarp, Hoppip, Wooper, Dunsparce, Treecko, Torchic, Mudkip, Meditite, Volbeat, Illumise, Wailmer, Spoink, Swablu, Budew, Minccino, Bunnelby, Fletchling, and Litleo. Volbeat or Illumise will also hatch from 2 km Eggs, depending on where you are.
5 km Eggs: Voltorb, Lickitung, Eevee, Ralts, Feebas, Clamperl, Blitzle, Roggenrola, Gothita, Solosis, Chespin, Fennekin, and Froakie. Certain other Pokémon will also continue to hatch from 5 km Eggs depending on where you are.
10 km Eggs: Nincada, Shinx, Gible, Riolu, Audino, Timburr, Darumaka, Emolga, Alomomola, Klink, Litwick, Axew, Golett, Rufflet, Espurr, and Noibat. Sigilyph will also hatch from 10 km Eggs, depending on where you are.