??? is a recurring character in the Legend of Zelda series. ??? is the name given to a person of unknown identity whose only visible body part is an arm. Although the only thing visible on ??? is his arm, it might well be that his body is located inside the toilet from which he sticks out his hand. He is in constant need of paper for a seemingly obvious reason.
The appearance of ???, or at least his hand, is similar to that of a Dexihand and a Floormaster from The Legend of Zelda: The Wind Waker. However, it is doubtful that they are related in any way.