How do you get to the secret island on animal crossing GameCube Without a GBA

There is no other way without a GBA.Unless there is a action replay code to get to it without a GBA.I don't know if theres a action replay code to get to it because i don't have a action replay for gamecube.If you have a action replay for gamecube, look for a code for it,but if you don't have a action replay,there is no other way.