Cannot take damage for the duration of the effect.
Can destroy objects, Obstacles, and Pitfalls without falling into them and open doors by walking into them. This includes metal blocks and key blocks without using keys.
Does not open challenge room doors or doors that require keys if you lack the keys.
Deals extremely heavy contact damage to enemies (80 per tick, or 2,400 per second).
This item belongs to the Fun Guy set. Collecting three items from this set will transform Isaac into a walking mushroom.
Notes[ | ]
Using Mega Mush again while its effects are still active will add an additional 30 seconds to the current active time.
Isaac's physical size, i.e. collision circle or "hitbox" is roughly doubled in radius when Mega Mush is active. This is the only item that can make Isaac tangibly larger than his starting size, as normal size ups can't increase the collision area beyond the default.
Mega Mush will not negate the damage taken from the Mausoleum door. It's even possible to die this way, while the item is active.
Non-tear based attacks such as Brimstone or Mom's Knife are overridden by normal tears while Mega Mush is active.
Isaac is unable to use the invulnerability effect to donate to Blood Donation Machines and Devil Beggars, since they will be destroyed on contact. Even Bomb Bums can be destroyed by walking over them.
If Isaac dies while giganitified, he will respawn in Gigantic form.
Synergies[ | ]
4.5 Volt: The contact damage dealt by Mega Mush will allow it to be recharged and used multiple times in the same room.
Car Battery: Mega Mush's active time will be doubled to 60 seconds.
Rock Bottom: Retains massive damage increase after Mega Mush's timer is up, though can make it nearly impossible to raise it afterwards without another use.
Serpent's Kiss: Enemies killed with contact damage will frequently drop hearts.
Mega Mush is based off of the Mega Mushroom from New Super Mario Bros., which would turn Mario giant, grant invulnerability, and allow him to defeat almost anything he touches.
Originally in Antibirth, the item didn't gain charges while active, and was unlocked by defeating Mother (then known as The Witness) as every character on Hard Mode.
Entering the Big chest in Mega Mush form triggers the credits 0.5 seconds faster than normal (tested by entering the Big Chest going from the same position to the beginning of credits and timed with scripts)
The Mega Mush form makes Isaac's face look similar to Flash Isaac.
Bugs[ | ]
Bug!
Activating Mega Mush before entering the Knife Piece 2 area will keep the effect active inside the chase area but Isaac will have his normal sized, followed with a huge shadow and will continuously stomp the ground, breaking everything in his way, even pushing away Mother's Shadow.
Bug!
If Isaac walks over a Teleport Pitfall while Mega Mush is active a visual bug will occur where the pitfall is destroyed and can no longer harm Isaac however its sprites still remain in the room. When Isaac reenters the room or exits and continues the run, the teleport pitfall works normally again.
Bug!
Using Mega Mush in combination with Suplex! makes you grab enemies and move them around until you leave the room. Doing this on any of the Ultra Harbingers or The Beast will make the enemy disappear and render you unable to move at all.
Bug!
Activating Mega Mush through Void will cause Isaac to visually revert to normal after leaving the room while still under the item's effects. If Isaac does not have flight, a stomping sound will play and the screen will shake constantly even if he is not moving.
Bug!
When Mega Mush times out and Isaac returns to normal size, he may occasionally appear to have no head. Isaac is unable to fire tears in this form and cannot interact with enemies or objects or pick up items. He also cannot interact with trap doors or Crawl Space entrances, causing softlocks. Going into an animation (e. g. by taking damage, using a pill, etc.), or exiting and continuing the run fixes this issue.
Pitfalls without falling into them and open doors by walking into them. This includes metal blocks and key blocks without using keys.
Bug!
Teleport Pitfall while Mega Mush is active a visual bug will occur where the pitfall is destroyed and can no longer harm Isaac however its sprites still remain in the room. When Isaac reenters the room or exits and continues the run, the teleport pitfall works normally again.
Suplex! makes you grab enemies and move them around until you leave the room. Doing this on any of the Ultra Harbingers or 
The Beast will make the enemy disappear and render you unable to move at all.
Void will cause Isaac to visually revert to normal after leaving the room while still under the item's effects. If Isaac does not have flight, a stomping sound will play and the screen will shake constantly even if he is not moving.
Mushrooms 
The Binding of Isaac: Rebirth
