Using a variety of exploits, the homebrew community has finally struck gold and figured out how to get it all going on the Wii.

With a SD card, Action Replay for the GameCube and SD card adapter for the GameCube, one can plug in their card into a computer, use some of that homebrew magic and get GameCube homebrew running on the console.

Of course, this could very well be a problem for Nintendo if folks use this exploit to run emulators (they will and, more than likely, are), bypassing the Virtual Console to play any ROM they wish.

link: Homebrew and Emulators on Wii
This is actually a way of playing Emulators on the Wii, using a Gamecube memory card.