Pokémon Red and Green launched on the Game Boy in Japan in 1996. These role-playing games introduced players to the central Pokémon formula: exploring a region, catching creatures, training them, battling other Trainers, and trading with other players.
The Game Boy was Nintendo's original monochrome handheld system, so the first Pokémon games were designed around its technical limits. Players could connect two systems with a Game Link Cable to trade Pokémon and battle. Trading was especially important because some species appeared in only one version.
Outside Japan, the games were rebuilt from the Japanese Blue version and released as Pokémon Red and Blue. The original Japanese Green version was not released internationally. Pokémon Yellow later became an enhanced version inspired partly by the anime, with Pikachu following the player rather than being stored immediately in a Poké Ball.
The Game Boy connection helped make Pokémon a social game as well as a solo adventure. Its hardware limitations did not prevent the series from becoming one of Nintendo's most successful franchises.