What accessory allowed players to trade and battle Pokémon in the original Game Boy games?

The Game Link Cable allowed players to trade and battle Pokémon in the original Game Boy games.

Pokémon Red and Blue used two Game Boy systems connected by the cable. Players could exchange Pokémon between versions or battle another Trainer, turning the series' collecting concept into a social activity that required another person and a second system.

Trading was not merely optional in the original games. Red and Blue contained version-exclusive Pokémon, so completing the original Pokédex required exchanging creatures between the two versions. The cable therefore supported both the competitive and collecting sides of the design.

Later Pokémon generations replaced the original cable-based system with new hardware and wireless features. The Game Boy Advance generation used a redesigned cable, and later Nintendo systems introduced wireless communication. Those upgrades can make the original accessory easy to forget, but the first-generation Game Boy games specifically relied on the Game Link Cable.