Instructions
Turn off your GameCube and unplug the GameCube controller. Before turning the GameCube back on, firmly plug the controller into the first controller port on the left side of the GameCube. The controller must be plugged in firmly to function properly, otherwise it may become unresponsive or function erratically from your on-screen character.
Plug in another controller in the same port to determine if the problem is with your controller or with your GameCube.
Reset the GameCube, being careful not to touch the yellow control stick on the controller as your game loads. If the control stick moves while the game loads, the control stick can become uncalibrated leading to erratic movement or camera placement in-game. A incorrectly calibrated controller often shows the same symptoms as a damaged controller.
Recalibrate your controller by pressing and holding the "X," "Y" and "Start" buttons for three seconds while playing your game. This resets and recalibrates it. In addition, unplugging and replugging your controller while the GameCube is on also recalibrates the device.
Clean your controller with a clean toothbrush and warm water. Unplug the GameCube controller. Lightly dip the toothbrush in the water and clean around the edge of the buttons, joysticks and directional pad. Dry your controller with a paper towel and allow it to sit for a few hours before plugging it back in.
Contact Nintendo's customer service through the Nintendo website to arrange for a repair or replacement of the device if your own troubleshooting efforts do not fix the controller.