When you pre-ordered Wind Waker a while back, you got a special limited edition disk that had the original OoT and Masters Quest on it, for gamecube. He could be playing that.
dont know if its the same as in the n64 but all you have to do is complete the water temple(dont know if you have to or not i did) get on top of the island where the entrance to the water temple is and stand on that big tile and shoot an arrow at the sun........pretty sure im correct, if not someone please correct me:D