Huge mushroom

The Huge Mushroom is a planned item or block which will be added in future versions, possibly beta 1.8. Huge mushrooms will appear in a new biome, and they won't appear in forests or other biomes unless they are planted.

History
In a tweet, Notch showed a picture of a 1.7 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 that 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 reveled a screen shot in Google+ in which a huge mushroom can be seen.