What accessory enabled Pokémon trading between two original Game Boy games?

The Game Link Cable enabled trading between two original Game Boy Pokémon games.

Pokémon Red and Blue used the cable to connect two Game Boy systems. Players could trade creatures that were exclusive to one version and battle one another directly. Completing the original Pokédex therefore required more than playing alone: some Pokémon had to be exchanged between different versions.

The cable supported the franchise's central idea that Pokémon could be collected and shared with friends. It also gave the games a competitive feature that did not require an internet connection. Players needed two compatible systems, two game cartridges and a physical cable connection.

The accessory is sometimes confused with later Nintendo hardware. The Transfer Pak connected Game Boy cartridges to Nintendo 64 games, while wireless adapters appeared in later Pokémon releases. The original Red and Blue trading experience depended on the Game Link Cable, a defining piece of early Pokémon history and a major reason the Game Boy games felt socially connected.