Mystery Box (item)
From the Super Mario Wiki
Paper Mario series
The first appearance of the Mystery Box 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:
These items can also be used for cooking, yielding a Mistake half the time, and a randomly selected one of twenty-three recipes otherwise.
Such items are on sale at Boo's Shop and the Bowser's Castle shop. They can also be found in a hidden block in the Shy Guy playground of Shy Guy's Toy Box, in a hidden block near the shores of Lavalava Island, and in the lava area of Bowser's Castle.
Paper Mario: The Thousand-Year Door
When used in battle, a Mystery has the effect of one of the following items:
Super Paper Mario
Mystery Boxes appear under their current name in Super Paper Mario. 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
Mario & Luigi: Dream Team
While Mystery Boxes do not appear in Mario & Luigi: Dream Team, another item known as a Secret Box with similar effects appears. Secret Boxes mimic a random badge effect, unlike Mystery Boxes, which mimic a random item.
Names in other languages