How to Use a Gamecube Controller on a Wii: 5 Steps (with Pictures)
Nintendo Support: How to Use Nintendo GameCube Controllers
Amazon.com: Dliaonew 2.4G Wireless Gamecube Controller, Classic Gamecube Wii Controller with Receiver Adapter for Wii Gamecube NGC (Pink and Blue) : Video Games
WiiMote prototype emerges with wires that let it plug into a GameCube - The Verge