Poison Mushrooms (also called Cursed Mushrooms) are mushrooms similar in appearance to a Super Mushroom and a 1-Up Mushroom, except of a slightly darker shade. Touching it in any game reduces the character's size (similar to the Mini Mushroom) or reverts the effects of any power-ups, and can also take off a player's life if he is small. In some games the Poison Mushroom looks similar to the Super Mushroom but they have the opposite effect and sometimes the Poison Mushroom will have "angry" eyes and a purple cap with a skull symbol instead of spots, such as in Super Mario Bros.: The Lost Levels. Sometimes, the poison mushroom will be purple, making is easier to spot and avoid. Depending on the game, they either damage or instant kill you.
In the Super Mario Bros Series
Super Mario Bros.: The Lost Levels
Originally appearing rather similar to the Super Mushroom, new players would discover to their dismay that these mushrooms were harmful. Later, changes were made which made them easier to tell apart from normal Mushrooms.
Poison Mushrooms make another appearance in Super Mario Bros 3. They appear in a single level and hide in grass instead of blocks.
Super Mario 3D Land
Poison Mushrooms also appear in Super Mario 3D Land, They only appear in special worlds. where they have a purple cap without a skull, and angry eyes. They emit a trail of purple gas, which is just for show. They steer themselves towards Mario, but if Mario reaches a place where the Poison Mushroom can't get at him, it will disappear.
Technically, Poison Mushrooms don't make an appearance in the game. However, in the four main settings in night mode, 1-UP Mushrooms turn into Rotten Mushrooms which will chase the character and try to kill them.
In the Paper Mario Series
Paper Mario: The Thousand-Year Door
Poison Mushrooms also appear in Paper Mario: The Thousand-Year Door, (with a slightly different design, Green with Purple spots instead of purple with pink) but not as items. When in battle, there is a chance that poison mushrooms will appear on the Bingo! wheel. If you match up three poison mushrooms, you and your partner will lose half your HP, and you will also lose half your FP and SP.
Super Paper Mario
Poison mushrooms appear as items, Poison mushrooms are useless on their own, poisoning the user when eaten, but can be used in many helpful recipies such as Trial Stew which gives the user experience depending on their current health.
Paper Mario: Sticker Star
Poison Mushrooms return in Paper Mario: Sticker Star in the form of sticker. The Poison Mushroom poisons both Mario and enemies for two turns. However, they are useless against poison-based enemies such as Poison Bloopers. They are one of the rarest regular stickers in the game. You can purchase one from a Toad behind the houses in Decalburg, purchase one from Whammino Mountain or find them sparsely hidden around in other levels. Mario needs one to access World 2.
In the Mario & Luigi Series
The enemy Trunkle will suck in a series of items which Mario and Luigi must dodge. Some of those items as Poison Mushrooms, which will poison either of them if they fail to avoid it.
Various enemies attack by either using or throwing Poison Mushrooms at the Mario Bros. These may alternatively be refered to as Shroob Mushrooms.
Poison Mushrooms replace Cheep Cheeps as one of Junker's attacks.
In the Super Smash Bros Series
Throughout the series of Smash Bros, beggining in Super Smash Bros Melee, Poison Mushrooms reduce the size and weight of the character who consumes it. This is detrimental as it means they would be knocked off the stage easier. They often appear to look like normal Mushrooms until eaten.
In the Mario Party series
The Poison Mushroom is a common item that appears in the Mario Party series. The Poison Mushroom is usually depicted with a dark blue-purplish color, with a skull cap and an angry face on the mushroom, like in Super Mario Bros: The Lost Levels. When a player receives a Poison Mushroom, their numbers on the Dice Block are usually reduced.
The Poison Mushroom debuts in Mario Party of this series. They are referred to as Poisonous Mushrooms and can only be obtained as one of two Mushrooms of the Mushroom Space (the other being the Super Mushroom). If a player is unfortunate enough to get a Poison Mushroom, they will lose the next turn.
The Poison Mushroom returns in Mario Party 2. In the board map Mystery Land, a player has a chance to summon a "curse" on another character by a Shy Guy. The character that receives the curse will have a Poison Mushroom placed on their head. When their next turn began, the high number they could get on the dice block is a three. The Poison Mushroom first appearance as an item was in Mario Party 3. In this game, a player could buy a Poison Mushroom from Baby Bowser's Item Shop for five coins, or win it in a Item Mini-game. When a player used a Poison Mushroom, their dice block was cut to only the numbers 1-3. The Poison Mushroom was very useful for landing on desired spaces that were only a few spaces away.
In Mario Party 4, the Poison Mushroom was replaced by the Mini Mushroom, which acted similar to the Poison Mushroom. When capsules were introduced in Mario Party 5, the Poison Mushroom was renamed the Cursed Mushroom, but still retained its original appearance. However, this time, the player would roll a 1-5 instead of a 1-3.
In Super Mario Party was appeare in Mario party of objets is going to roll the dice giving -2 for this objet