One hardware modder has figured out a way to hook up a Nintendo GameCube controller to a 2DS/3DS console.
Using an old capture board, 3DSCapture member Loopy managed to link-up a GameCube controller to a 2DS console, with the analogue stick mapped to the d-pad and the C-stick mapped to the face-buttons. In the video demo, Loopy plays through Super Street Fighter IV using the controller.
Would you like to hook up a 3DS controller to the hardware?