Is there a reason why mic input is only visible for Pads 1 & 2, and not 3 & 4?
The
microphone on the gamecube uses the memory card slot. As the gamecube has two memory card slots, and the button is on the microphone, the button is configurable on the first two gamepads only...
A good reason: There are only two MC slots on a GC so you can only plug two mics
EDIT: beaten by Mister skid