Well, today I finally dug out my old gamecube to get the controllers from it. Now I did a quick search here and saw nothing about it. The reason why I'm posting is because apparently MadCatz GC controllers don't work on GC done on the Wii. Now I only have one MadCatz controller, and its possible its a bad controller, but I wanted to give heads up anyways.
My normal controler worked perfectly fine.
P.S. The GameCube graphics look pretty crappy compared to Wii graphics. Still awesome games though. I just really didn't think it was that big of a difference between the two systems, guess I was wrong.