Generation II introduced 100 new Pokémon in Pokémon Gold and Silver.
These games added the Johto region and expanded the National Pokédex from the original 151 species to 251. The new group included familiar favorites such as Chikorita, Cyndaquil, Totodile, Lugia, Ho-Oh, and Celebi.
Gold and Silver also introduced several important mechanics. They added the Dark and Steel types, Pokémon eggs, breeding, baby Pokémon, held items, day-and-night cycles, and different-colored Shiny Pokémon. The games were designed as sequels and allowed players to revisit Kanto after completing the Johto adventure.
The number is sometimes confused with later generations, which introduced different totals. Generation VI added 72 species, while Generation V added 156, the largest single-generation increase. Generation II remains especially notable because it connected a new adventure to the original region.