Chunsoft developed Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team.
The paired games were the first releases in the Pokémon Mystery Dungeon series. Red Rescue Team was made for Game Boy Advance, while Blue Rescue Team was made for Nintendo DS. They were released in Japan on November 17, 2005, and reached other regions in 2006.
Unlike the main Pokémon role-playing games, Mystery Dungeon titles use a roguelike structure. Players explore randomly generated dungeons, move through turn-based encounters, collect items, and recruit Pokémon to a rescue team. The player character is transformed from a human into a Pokémon.
Chunsoft was already known for the Mystery Dungeon genre before working with Pokémon. The company later became part of Spike Chunsoft, but the original Rescue Team games were developed under the Chunsoft name. Game Freak, by contrast, developed the mainline Red, Green, Blue, and later generation games.