From the Super Mario Wiki
Mushrooms are items which restore players' health. They are most prominent in the RPGs.
Super Mario Bros. 2
Mushrooms add an additional mark or heart to the life meter, to a maximum of four. The meter then resets to two marks at the start of the following stage. Up to two are located in each stage, and are found only in specific Subspace locations within the stage. In Super Mario Advance, an extra mushroom is added to each level to bring the maximum total to five hearts.
The equivalent to the Mushrooms in Yume Kōjō: Doki Doki Panic are hearts.
Mario Kart series
In the Mario Kart games, a Mushroom is an item that grants a Kart a short speed boost when used. Mushrooms can come in singles or triplets, the latter providing three Mushrooms to use in a row. In Mario Kart: Double Dash!! a character holds these mushrooms in piles, but if the kart is hit by an item on the road, these mushrooms will fall off and the character will have one remaining on hand. Normally this set appears as default power-ups in time trial mode (excluding Super Mario Kart) to use specially over shortcuts of a determined course. Another type of Mushroom is the Golden Mushroom, that can be used indefinitely in a restricted period of time. One can optionally be used for the Mario Kart 64 shortcut.
In recent Mario Kart games, Mushrooms can be used as well to knock aside other karts or even steal an item from opponents by ramming them, as seen in Double Dash!!. In later games, this move cannot steal items, but works to steal balloons, Shine Sprites or coins from other players when playing in battle mode.
The Mushroom is also used as the logo for the Mushroom Cup in every Mario Kart game to date.
In the European and Australian versions of Mario Kart 7, they are called the Dash Mushroom and Triple Dash Mushroom. Also in Mario Kart 7, there is a large mushroom in the cave of Rosalina's Ice World.
In certain games, it can be used to avoid the Spiny Shell (Mario Kart), however, it is hard to obtain the Mushroom in 1st place.
Super Mario RPG: Legend of the Seven Stars
In Super Mario RPG: Legend of the Seven Stars, a basic Mushroom can be accumulated in the inventory and recovers 30 HP for one party member. This Mushroom has a red and white cap with an orange stem and no face. However, Mushrooms that have faces are found in Treasure Boxes, and they automatically recover all HP and FP for Mario's entire party once uncovered. Most of these Treasure Boxes restock once the area is entered again. Other types of Mushrooms exist, including two other increasingly expensive kinds used for basic recovery. The Mid Mushroom recovers 80 HP to one party member, and they have a green cap rather than a red one. The Max Mushroom is able to recover all HP to one party member and has a yellow cap. In the Japanese version, the Mid Mushroom and Max Mushroom are respectively known as Super Mushroom and Ultra Mushroom, which would become the terminology used in future RPGs.
There are Mushrooms indistinguishable in appearance but instead cause negative effects on allies and adversaries alike. The Bad Mushroom, only found in Seaside Town, does not recover HP and is used only in battle. When used, they poison an enemy of choice, but some enemies are resistant. Another Mushroom is sold by the Goombette Triplets at the shop in Monstro Town. These Mushrooms, apart from restoring 30 HP, actually turn the user into a Mushroom (a status ailment also caused by certain enemy actions). While a Mushroom, the character recovers health every turn, but is completely immobilized.
Mario Party series
Mushrooms appear as items in the Mario Party series. The first time they appear is in Mario Party 2 (where they are Mario's favourite item), and they have reappeared in other Mario Party titles. In Mario Party 4, Mario Party DS, Mario Party 8, and Mario Party 9, the item is not present (although there are similar items, such as Mario Party 4's Mega Mushroom, and Mario Party 8's Twice Candy). They allow for two rolls of the Dice Block during one turn. If the two digits rolled are the same, the user will receive ten Coins. If players want to purchase this item, the price will usually be five Coins.
In Mario Party Advance, their effect is different. In this installment, Mushrooms allow the player to roll the Dice Block. Each turn, a Mushroom will be depleted from the stock. For players to win Mushrooms, they have to win minigames. Players will usually receive three Mushrooms when they win a minigame, although there are cases in which the award for winning a minigame will be six Mushrooms. The game ends when the player doesn't have any Mushrooms left.
In Mario Party: Island Tour, they're referred to as Dash Mushrooms, and allow the player to add three spaces to the Dice Block total.
Mario & Luigi series
Mario & Luigi: Superstar Saga
Mushrooms are the basic item for healing in Mario & Luigi: Superstar Saga. They are the cheapest item found in stores and the first item obtained. Their colouring is reversed in this game, with their caps being white with red spots; they also lack faces. Regular Mushrooms restore 25 HP, Super Mushrooms restore 50 HP, Ultra Mushrooms restore 120 HP, and Max Mushrooms restore all HP. Five special Golden Mushrooms can also be found in the game; the rare item restores all HP and BP. Shroom Badges that can be purchased at certain shops will increase Mario and Luigi's attack according to the number of Mushrooms in their inventory.
A unique mushroom called the Invincishroom (a mix of 1-Up Mushrooms and Stars) can be found only when the player has beaten the high score of a certain minigame. The player cannot use it, however, because Mario eats it as soon as he and Luigi win it, causing him to become very sick and slowly turn into a bean. Luigi cures Mario by giving him Crabbie Grass, which is found in Guffawha Ruins.
Mario & Luigi: Partners in Time
Mushrooms act in the same manner as in Mario & Luigi: Superstar Saga; they restore HP for one member. While the Max Mushroom is still the same, the regular, Super and Ultra mushrooms heals 20HP, 40HP and 80HP respectively. In Mario & Luigi: Partners in Time, there are also items called Mushroom Drops, which will heal every single member on the team, very much like the Nuts in Mario and Luigi: Superstar Saga. Unlike Max Mushroom and Max Nuts, however, there is nothing more powerful than Ultra Drops. Shroom Badges make a return, but with a different effect: they now increase the healing effects of a Mushroom.
Shroobs, the main enemies in this game, bear a resemblance to Mushrooms. They have the same mushroom shape and spots, and they even live on a planet shaped like a mushroom.
Mario & Luigi: Bowser's Inside Story
Mushrooms return in Mario & Luigi: Bowser's Inside Story, but Mushroom Drops are replaced in favor of the original Mario & Luigi series Nuts. Mushrooms act in the same manner as in the two preceding games. Mushrooms in this game heal 30HP, Super Mushrooms heal 60HP, Ultra Mushrooms 120HP, and Max Mushrooms heal 240HP instead of all HP like in the previous installments.
Also, there was a Clothing item called the Mushroom Glove, which would have a random mushroom be consumed every turn to the bro. that has the glove. Bowser does not eat mushrooms unless a Goomba/Bob-omb from a Jailgoon, a Trashure or Dark Trashure, or a Naplock gives him one, or he uses Refreshrooms, which recover half of his Health Meter (only when he is Giant Bowser).
Mario & Luigi: Dream Team
Mushrooms return in Mario & Luigi: Dream Team, and this time, it can be used anywhere. Regular Mushrooms heal 30 HP, Super Mushrooms heal 60, Ultra Mushrooms heal 100, and Max Mushrooms heal 160. If Shroom EXP is used, then the value of the HP healed from using Mushrooms during battle will be converted to EXP at the end, but with a 50% bonus. Regular Mushrooms add 45 EXP, Super Mushrooms add 90, Ultra Mushrooms add 150, and Max Mushrooms add 240.
The game also introduces a special technique that involves the use of Mushrooms called Rhythm Mushroom, which is exclusive to giant battles.
Paper Mario series
In Paper Mario, Mushrooms take the role as healing items, similar to other Super Mario RPG games. In this game, they heal 5 HP when used. Several variations of Mushrooms could be found, such as the Volt Shroom or the Life Shroom. Recipes can also be made for other types of Mushrooms by combining certain ingredients together by Tayce T.
Paper Mario: The Thousand-Year Door
Mushrooms return in the Paper Mario sequel, Paper Mario: The Thousand-Year Door. They heal in the same manner as in the previous game, with the addition that - now that Mario's partners have HP - mushrooms can restore a partner's HP also.
The many variations of Mushrooms from the previous game return, with the addition of the Slow Shroom. Small creatures named Punies commonly eat Mushrooms, shown by brother and sister Punio and Petuni. At the end of the game, Punio and Petuni give both Mario & Peach a Mushroom to enjoy on their boat ride home.
Super Paper Mario
Super Paper Mario is a platformer RPG game, so unlike in the preceding games, Mushrooms cannot be bought in shops. Instead, they are found out of ? Blocks and heal ten HP upon contact. They also give the player one thousand points. Replacing them is the Shroom Shake.
Paper Mario: Sticker Star
In the latest installment of the Paper Mario series, Paper Mario: Sticker Star, Mushrooms appear, much like every other item, as stickers. They restore 20 HP, but if the button is pressed with good timing, the effect can be increased to 30. Two stronger Mushroom stickers also exist: the Shiny Mushroom, which acts like a Super Shroom, which restores 40 or 60 HP, and the Flashy Mushroom, which acts like an Ultra Shroom, which restores 80 or 99 HP. Big 1UP and Big Shiny 1UP stickers also appear, restoring 10 or 15 HP for 10 turns, respectively, and Poison Mushrooms, which poison Mario, but enemies also get poisoned if they touch him.
Mario Golf: World Tour
Mushrooms appear in Mario Golf: World Tour as usable item shots. They cause the ball to roll much farther along the ground, as well as with a blue streak.
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