Mega Mushroom is an item that appears in the games Mario Party 4, Super Mario 64 DS, New Super Mario Bros. and Mario Kart Wii. the Mega Mushroom turns you into an enormous version of yourself for a small amount of time, crushing everything and everyone in your path.
 Mario Kart Wii
Speed boost, ability to crush and stall some hazards, protection from lightning.
A Warning will show at the bottom of your screen saying a Mega Mushroom is appearing, stay to the side or make sure the bubble isn't in the middle when it comes near you.
DO NOT charge everyone around you, but don't avoid people. Instead, use the mushroom to take shortcuts that require a mushroom or star.
 Mario Party 4
2 Dice Blocks. Let's you crush others in your path and take 10 coins away from them. Costs just 5 coins to buy.
Bypass ALL board events including Item Shops and Star spaces.
You can either use them when you're near your foes or save them to have something to get payback on an opponent who uses this and takes coins from you.
Light shade of green.
 New Super Mario Bros. 2
It would return in New Super Mario Bros. 2 after not being in New Super Mario Bros. Wii. The Mega Mushroom would work the same as it did in New Super Mario Bros. though the player will not earn 1-Up Mushrooms for their destruction.