The Poison Mushroom (毒きのこ, Doku kinoko) is an item in Super Smash Bros. Melee and Super Smash Bros. Brawl. It is similar in shape to the Super Mushroom, but has a duller cap and "frowning" eyes. Instead of making the character larger, the Poison Mushroom shrinks any character that touches it. The Poison Mushroom's effect lasts for about 10 seconds. The Poison Mushroom induces the following effects on those who touch it:
Poison Mushrooms made their first appearance in the Japanese version of Super Mario Bros. 2 (later released in North America in Super Mario All-Stars as Super Mario Bros.: The Lost Levels). If a player is small and touches a Poison Mushroom, the player loses a life. When the player is big and touches a Poison Mushroom, the player turns back to normal. The Poison Mushroom in Melee and Brawl shrinks whoever touches it. The Poison Mushroom shrinking players could be a reference to how they made "big" players turn back to being "small".
 Melee trophy
Poison Mushrooms made their debut in Super Mario All-Stars, where they'd cost characters a life if picked up. These nasty fungi are dark and foul-tasting, and in Super Smash Bros. Melee, they make you shrink on contact. With your diminished stature comes a loss of power and mass, making you a prime target to get smashed offscreen with even a light attack.
 Brawl trophy
A penalty item that shrinks whoever grabs it. It's hard to distinguish from a Super Mushroom, so you may find yourself getting small when you wanted to get big. When you're in miniature form, your attack power drops, and even the lightest attack can send you off the stage. That being said, a small target's hard to hit. Your best plan when you're tiny may be to run.