Kris is the first playable female protagonist in a main Pokémon game.
She was introduced in Pokémon Crystal, the enhanced version of Pokémon Gold and Silver released for Game Boy Color. Crystal allowed players to choose a female player character for the first time in the core series.
The earlier games offered only a male player character, even though players could name him themselves. Kris's introduction made the player's avatar more explicitly customizable and helped establish gender choice as a recurring feature in later main-series games.
Kris is sometimes confused with May, the female protagonist associated with Pokémon Ruby and Sapphire. May was the first playable female character in Generation III, but Kris appeared earlier in Generation II's Pokémon Crystal.