LINK CABLE for Nintendo Game Cube/Game Boy Advance! It works on Nintendo Wii too in Game Cube games only.

This cable connect the GBA on Game Cube Games that support this feature: it can be used as a secondary screen or as an alternative controller or to unlock secrets in GBA or Game Cube games (for example: Metroid Prime, The Legend of Zelda Wind Waker, The Legend of Zelda Four Swords, Animal Crossing, Wario Ware Inc., Final Fantasy Crystal Chronicles etc.).