Bug: If you stand in front of a bug or a fish and press start right after swinging a bottle at it, you can put another item in the bottle's place and turn it into another bottle. When this happens, the erased item cannot be recovered, and the new bottle will retain the limitations of the original item (for example, turning the Claim Check into a bottle will still be unable to be used by Young Link.).
Bug: For both the Nintendo 64 version and the Nintendo 3DS version. Go inside the Thieves' Hideout in Gerudo Valley and look for a pot that is boiling. When you do, stand next to it and Navi will appear and turn green indicating that there is something hidden there. However, playing any song on the ocarina will not make anything appear.
Answer: Because the Kokiri don't age past a certain age, but they do age up to that age. Link looked roughly the same age as the other Kokiri when his adventure started, which is why they never noticed that he was different.