??? is one of the weirdest inclusions in the Zelda series, but that’s what makes them memorable. First appearing in Majora’s Mask, and then Oracle of Ages, this strange character is in constant need of paper. We know very little about them, other than the fact that they’ve appeared in a toilet each time.
Link is able to trade goods with ??? in each game, with a piece of heart being available in Majora’s Mask, and a stink bag in Oracle of Ages. ??? doesn’t otherwise play a huge role in Link’s adventures, but they stick with us purely because of how unique and weird they are.