Java Edition 2.0

On April 1, 2013, Mojang announced Minecraft 2.0 as an April Fools' Day joke. An actual version was distributed to select celebrity individuals. The version has not yet been officially made available to the public, however the download link and jar file can be accessed by the public and be downloaded and played from assets.minecraft.net.

Downloads
There are different download links that correspond to three different versions.

Changelog
http://mojang.com/2013/04/its-finally-coming-minecraft-2-0/

Bugs

 * Tinted glass has a bug where if on fast graphics, the bottom has some texture glitches when placed on any surface except Air.
 * You cannot see water through tinted glass.
 * You walk faster on Etho Slabs.
 * Mooshrooms can spawn regular cows with mushrooms on their back.
 * Coal retrieved from Coal Blocks doesn't stack with normal coal, because it has a different data value (32767 as opposed to 0)

Trivia

 * At 8:00 New York City Time, the splash text in 2.0 now will be huge and say APRIL FOOLS! in pink letters and obstruct the title menu.
 * Some features that were not noted in the changelog were these 2:
 * Mobs can have a rare chance of escaping fences and thin glass, and smaller mobs have a larger chance.
 * Blocks and mobs can talk using speech bubbles. Quotes include "You punched me!" "You mined me!" and "Mommy?" (Mummy? For people in the UK)
 * Etho slabs (TNT Slabs) have a bigger explosion than TNT, although they are smaller than TNT.
 * Tinted glass uses filters.
 * A new mob, the Friendly Wither, (Sometimes referred to as the Pink Wither) was added. To spawn it, place a pink wool block, put a Flower pot on top, and a rose in the Flower pot.  Feed it sugar to grow it some heads.
 * Droppers are renamed to floppers, and will change anything they drop to a fish.