Every new season, new Pokémon join the game. Below is the list of the new pokémon that debuted in season 2 or 3 in order in which they appeared in:
Season 2[]
Tangrowth
Milotic
Grumpig
Zangoose
Lunatone
Castform
Toxicroak
Carnivine
Gliscor
Luvdisc
Leafeon
Flygon
Medicham
Lumineon
Unown
Persian
Girafarig
Shaymin
Dugtrio
Rampardos
Season 3[]
Jolteon
Smeargle
Marowak
Mothim
Starmie
Roserade
Meganium
Banette
Phione
Weavile
Hitmontop
Ambipom
Onix
Teddiursa
Lapras
Glaceon
Honchkrow
Drapion
Froslass
Absol
Shuckle
Uxie
Mesprit
Azelf
Probopass
Mamoswine
Vaporeon
Flareon
Tropius
Illumise
Shiny Illumise(Ella)
Stantler
Dragonite
Togetic
Goldeen
Xatu
Lickitung