Which Pokémon games introduced Shiny Pokémon?

Pokémon Gold and Silver introduced Shiny Pokémon to the main video-game series.

A Shiny Pokémon is an unusually colored version of a regular species. In the games, its status is determined when the Pokémon is generated, whether it appears in the wild or hatches from an Egg. Shiny Pokémon also produce a sparkle effect when they enter battle.

The feature debuted in the 1999 Game Boy Color games Pokémon Gold and Silver, the second generation of the series. The famous Red Gyarados encountered at the Lake of Rage gave many players their first guaranteed encounter with a Shiny Pokémon.

The original games made Shinies extremely rare: the standard encounter odds were 1 in 8,192. Pokémon X and Y, released in 2013, reduced the standard odds to 1 in 4,096. The term “Shiny” began as fan terminology and was later adopted officially.