??? (Majora's Mask)

??? is a gray-colored hand that seems to live inside of toilets wherever it (he?) is found.

Majora's Mask
After midnight in Majora's Mask, it reaches out of the toilet next to the reception door at the Stock Pot Inn. In return for a piece of paper (i.e. one of the Title Deeds, Anju's letter to Kafei, or Express Mail), ??? will reward you with a Piece of Heart.

No one knows the true origin or name of ???. It might be speculated that perhaps this person fell in and couldn't get out, or maybe it's a nod to the mini-boss (Dead Hand) in Ocarina of Time's "Bottom of the Well" mini-dungeon that had hands like these pop out of the ground.

Oracle of Ages
In Oracle of Ages, in the past, ??? is another gray hand that needs toilet paper. If you give the Stationary to him, as part of a trading sequence, he will give you a Stink Bag which is needed to clear the sinuses of a Tokay Cook. You can torture him in various ways, such as putting seeds in the hole he dwells in.
 * Mystery Seed: "Wh-What?!?"
 * Ember Seed: "Ooo... hot!"
 * Scent Seed: "Ewwww!"
 * Gale Seed: "My head spins!" (This can only be done by using the Roc's Feather to jump over the hole and dropping the seed before falling.)
 * You cannot use a Pegasus Seed on ???.
 * If you push the chamber pot into the hole: "Nooooo!"
 * Bomb: *explodes* "Koff!"
 * Bombchu:"???" *explodes* "Koff!"