While essentially both titles were or offered multiplayer capabilities, you had to know someone with the game cartridge (Four Swords) and a GBA plus connecting cables.
Looking ahead to 2004, titles like the Puzzle Collection, Pacman, Pokemon Colosseum and The Legend of Zelda: FourSwords will take advantage of the ability to connect GameCubes to GameBoys.
In Zelda FourSwords, for example, players will be able to explore Hyrule on the TV then pop underground on their GameBoys to uncover secrets which will help in the game.