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.
A new feature called the PokéGear appears that has the capabilities of a mobile phone, allowing trainers to challenge you to a rematch, and radio, with various radio shows and music.
Some Pokémon are updated with new types or characteristics (Magnemite and Magneton become Electric/Steel type, for example).
In-battle weather effects are added.
Ghost-type attacks are super effective against PsychicPokémon. Poison attacks do normal damage to Bug Pokémon, Bug attacks now do half damage to the PoisonPokémon. Ice attacks are now ineffective against FirePokémon.
Some attacks have changed their type, e.g. Bite changed from Normal to Dark type. New movements are added, highlighting the Bug to balance the weaknesses of Psychic-type Pokémon.
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.