Game Boy Player
The Game Boy Player was an official add-on by Nintendo. It gave the user the ability to play Game Boy, Game Boy Color, and Game Boy Advance games on the GameCube. It required not only the hardware itself (which must be attached to the bottom of the system by removing ay covering of the hi-speed port from the back-right), but a special mini-disc to run the software needed to activate the functionality; without it, the hardware can't actually do anything unless unofficial means such as homebrew are used (e.g. swiss-gc).