Huge mushroom

The Huge Mushroom is a naturally occurring structure which was added to the game in Beta version 1.8. Huge mushrooms can be destroyed to drop more regular mushrooms of the same type. They are composed of several blocks: mushroom stalks and either red or brown colored blocks for the head. You cannot grow a Huge Mushroom above the height limit/skybox without modifying the game.

In Beta 1.8, you can make them grow by using Bone Meal on normal mushrooms only if the mushroom was planted on dirt. It is currently unknown if normal mushrooms can become huge mushrooms another way. Both the blocks making the stalk and the head of huge mushrooms can be quickly destroyed by hands and drop 0-2 normal mushrooms.

When growing huge mushrooms indoors, the brown requires at least a 9x9x8 room and the red a 7x7x8.

Interestingly enough, the texture of huge mushrooms' caps depends on their position on it. For example, the corner block of a giant brown mushroom hat has 3 sides with the brown texture and 3 sides with the pore texture, while a block in the middle of the cap has only its top face covered with the brown texture, the others being the pore texture.

History
In a tweet, Notch showed a picture of a 1.8 change-list. Although it was completely blurred out and was, at first, thought of as a joke, but then Notch stated that one of the pictures with the new lighting system and the change list had a secret in them. People all around the web started speculating.

One place that people discussed it was on the Minecraft forums, where it was discovered that the tabs at the top of the change list, which were partly covered, could be decoded based on the one pixel tall pattern available in the image.

After a user named "tmcaffeine" successfully decoded, the tabs read: ExperienceOrb.java, changelist.txt, Level.java, Tile.java, HugeMushroomTile.jav(a?), HugeMushroomFeature.(java?), RandomLevelSource(cut) that led people to speculate that huge mushrooms will be added, and indeed, later on Notch revealed a screen shot on Google+ in which two huge mushrooms can be seen as well as an NPC Village.

In the 1.8 pre-release, huge mushrooms did not generate naturally, but could be planted by the player by using Bone Meal on a red or brown Mushroom. In the pre-release version 1 of 1.8's Creative Mode, since the blocks composing a huge mushroom and bonemeal were not included in the item selection menu, the only way to create huge mushrooms is to give yourself regular Mushrooms and Bonemeal, then planting the mushroom, then using the bonemeal on the mushroom.

Farming
Huge mushrooms can be grown using bonemeal and then destroyed to drop more small mushrooms. It is possible to continue to grow and destroy the mushrooms for produce, so long as enough bonemeal is available. As each giant mushroom can be expected to drop two dozen or more small mushrooms, two bonemeal can be used to generate potentially a hundred or more points of hunger bar, making them something of a miracle crop.

Huge mushrooms are destroyed faster wielding a sword. Bonemeal will not grow a mushroom into a huge mushroom in the presence of a torch.

Trivia

 * Planting a Mushroom on any block and growing it with Bone Meal changes the block to dirt. In Beta 1.8 pre1, mushrooms did not have to be on dirt or grass to be able to grow, so this could be used on Bedrock, making a quick and easy way to get to The Void without hacking.
 * Huge Red Mushrooms can be used to build a basic hut, either by filling in the space between the cap and the ground, or by digging a large enough hole to accommodate a Huge Mushroom so that the cap intersects with the ground (may take multiple attempts).
 * Carrying brown mushrooms and bonemeal gives explorers the ability to quickly assemble platforms out of Huge Brown Mushrooms, which affords a sleeping platform safe from mobs when illuminated (a single torch in the center is sufficient).
 * Huge Mushroom blocks cannot be acquired normally in Survival Mode, but it is possible to manipulate the blocks from huge mushrooms with pistons.
 * If you hack in huge mushroom blocks into the game they can be used in a furnace, burning as long as wooden planks.
 * If created by hacking instead of normally, the spore texture appears on all sides of their blocks, as this is the default data value for the block, similar to how white wool works.
 * Huge Mushroom stalks give off a light level of 2. You can see the light if you go inside a huge red mushroom and block off the gaps.