Poison Mushrooms are items that are dropped by Portrait Ghosts and found in drawers, cabinets etc. When dropped, they bounce frantically and unpredictably, making it hard to avoid them in small areas. When collected, they will shrink Luigi, making him unable to use his Poltergust 3000, thus leaving him to have to use his flashlight to fend off ghosts, and forces him to drop a few Coins. After a few seconds, the effect will wear off, and he will return to normal size.
- While small, Luigi's voice is high pitched, which is easy to hear by calling out for Mario by pressing the A button. This is also the only action that Luigi can perform while under the effect.
- Portrait Ghosts usually drop the poison mushrooms around 20 HP, to stop Luigi getting the Big Pearl for the gold frame.
- There is an unused animation for the poison mushroom rather than shrinking luigi is choking and showing depressed eyes this also causes luigi to lose HP.