Generation II added 100 new Pokémon species to the main video games.
The additions debuted in Pokémon Gold and Silver, with the enhanced Pokémon Crystal following later. They expanded the Pokédex from Generation I's 151 species to a total of 251.
Generation II introduced the Johto region and added features such as Pokémon breeding, a day-and-night system, held items, and the Dark and Steel types. Several new species also connected to earlier Pokémon through baby forms and evolutions.
The figure is sometimes confused with the total of 251, which counts both generations together. It is also distinct from Generation III's 135 new species. In generation counting, “new Pokémon” means species debuting in that generation, not the complete cumulative Pokédex.