Generation II (also known as the metal or precious metal generation) is the second generation of Pokémon games, and sequels to the original Generation I games Red and Green (Red and Blue for international players).
Generation II was the first Generation where Pokémon began to expand, introducing 100 new Pokémon which could not be found in the original Generation I games. Many of these Pokémon expand the evolution families of older Pokémon, while a majority of them are brand-new evolutionary families.
These games were initially called "Pocket Monsters 2". Generation II events occur three years after Generation I, and occur simultaneously with the events of Generation IV.
The ability to find differently colored Pokémon, Shiny Pokémon, is added.
Possibility to visit Kanto years after Red/Blue/Yellow, with trainers with high levels, the opportunity to complete the eight Gyms in Kanto (being 16 in total in the game), and the ability to fight both Blue, or the rival from the previous generation and Red, the protagonist of the previous generation.
In Crystal, a female player character, Kris, can be chosen for the first time.
In Crystal, moving sprites are given to opposing Pokémon and Pokémon on their stats page.
Gold, Silver and Crystal feature infra-red connectivity to the Pokémon Pikachu and Pokémon Pikachu 2 pedometer using the mystery gift feature.