The Pokémon Mystery Dungeon series first released in 2005.
Its first games were Pokémon Mystery Dungeon: Red Rescue Team for Game Boy Advance and Pokémon Mystery Dungeon: Blue Rescue Team for Nintendo DS. Both launched in Japan on November 17, 2005, before receiving worldwide releases in 2006.
Unlike the main Pokémon role-playing games, Mystery Dungeon places the player in randomly generated dungeons with turn-based movement. The player character is a Pokémon, and the story focuses on rescue teams, missions, recruitment, and exploration rather than traveling between conventional Gyms.
The year is often confused with 2006 because that was the international release year for the original pair. It is also easy to mistake the series for a single game, but Red Rescue Team and Blue Rescue Team were companion releases on different Nintendo handhelds.