Reverse Mushroom
A Reverse Mushroom is an uncommon type of Mushroom. It is the opposite of a Super Mushroom, causing someone who is enlarged to shrink and vice versa. This mushroom can be used against foes.
It made its debut in the Battle Mode found in the main menu of Super Mario Bros. 3 (Super Mario All-Stars version), where it would reverse the two players' positions on the screen or reverse their super/small forms.
It also appears in Mario Party 3. It is green with a red U-turn symbol on it and is Donkey Kong's favorite item. The player who has it can make any player on the board (including himself/herself) go in reverse when they are moving across it, until they reach a fork or area with multiple paths, then the person inflicted can choose to go forward in another direction, or still go backwards.