|Kind of Item||Mushroom|
|First Appearance||Super Mario World: Wii|
|Latest Appearance||New Super Mario Bros. D.I.Y|
|Takes a life from Mario away, hence the name.|
| 1-Up Mushroom|
1-Down Mushrooms are harmful items that subtract an extra life from Mario's life counter, the opposite effect of the 1-Up Mushroom. Whether this also immediately kills Mario depends on the game. They are based on the Poison Mushroom, which does the reverse of a Super Mushroom.
The appearance of the 1-Down Mushroom varies extremely. Some are obviously poisonous based on their color scheme, while others look only slightly different from real 1-Up Mushrooms.
A similar item, the Poison 1-Up, is mentioned in Super Paper Mario as the cause of death of a Shayde in the Underwhere. It is possible that this was a mistake by the localization team and that they were referring to the Poison Mushroom.
- Super Mario World: Wii
- New Super Mario Bros. Omega
- New Super Mario Bros. D.I.Y.
- Super Mario Bros. HD
- 1-Down Mushrooms in New Super Mario Bros. Omega have references to the Super Mushroom. At first, it has red spots (like a Super Mushroom's cap is red), while the 1-Down Mushroom's cap is dark cyan (cyan is the inverted RGB color of red, this color is dark for being a negative item).
- Red is the inverted RYB color of green, showing its inverted effect of a 1-Up Mushroom.
- The 1-Down Mushrooms in New Super Mario Bros. D.I.Y. is styled after the Poison Mushroom from the Super Smash Bros. series, hence the dark-pale lime-green color.
- The Poison Mushroom in Super Mario World: Wii has the same colors as a 1-Up Mushroom, only switched. Instead of having a green cap, they have a white cap. Instead of white spots, it has bright green spots.
- This makes the Mushroom resemble a Green Toad.