Huge mushroom

The Huge Mushroom is a planned naturally occurring structure which will be added in future versions, possibly beta 1.8. Huge mushrooms will appear in a new biome called the Swamp Biome, and they won't appear in forests or other biomes unless either a Red Mushroom or a Brown Mushroom is planted and Bone Meal is used. These huge mushrooms can be destroyed to drop more regular mushrooms of the same type. They will be 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.

Both the Huge Mushrooms will be added into the 1.8 Beta update.

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

By implementing the above method, the block that the mushroom had been placed on will transform to dirt, no matter what type of block it is placed on. This could be abused to slowly dig yourselve through bedrock.

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 hat 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. Huge mushrooms could also not be created using any method in the pre-release of 1.8's Creative Mode, as the blocks composing a huge mushroom were not included in the menu with all of the blocks in it, and although you could give yourself regular Mushrooms, you could not give yourself Bone Meal. However you can place the Crafting Table and then give yourself Bones, thus allowing you to make them in Creative Mode.