A Mystery is an item found in Paper Mario, Paper Mario: The Thousand-Year Door, and Super Paper Mario.
 Paper Mario
The first appearance of the Mystery item in Paper Mario goes under the name Mystery?. When used in battle, a roulette will appear, containing the following items, that will be used right after the roulette stops on an item:
Mysteries can also be used for cooking, but the player must be aware that the item used in the recipe when he gives the Mystery will be random, so the item may generate a Mistake if the player is unlucky.
 Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, Mystery is sold for three coins at Niff T.'s Item Shop and Pungent's Shop. When used in battle, a Mystery makes a completely random item appear that could be anything from a Poison Shroom to an Ultra Shroom to a Shooting Star. If it is cooked with a Point Swap, it makes any recipe.
 Super Paper Mario
Mysteries appear once more in Super Paper Mario, this time under the name Mystery Box. When cooked, the outcome can be random, or more commonly, a Mistake. However, the set recipe is a Miracle Dinner. The Mystery Box can be bought in Flipside Arcade for five Flipside Tokens, at the Downtown of Crag for three coins, or carried by a Lakitu. Similar to Paper Mario: The Thousand-Year Door, a random item will appear which can be any item from a Catch Card to a Thunder Rage.
 Paper Mario: Sticker Star
The Mystery item was originally set to re-appear in Paper Mario: Sticker Star for the Nintendo 3DS, as seen in early artwork. However, this item was removed for unknown reasons.
 Names in Other Languages
||Who knows what it is