http://us.battle.net/hearthstone/en/What do you guys think? We have only recently received info on this, Blizzard has a history of great april fools jokes but this one getting started before april makes me wonder if it counts
Here are some previous april fools jokes from them:
The Bard, was revealed to us as a new class that would use guitar hero controls.

Mount customisation:

and my fav, the molten core game:
Some of these jokes have actually made it into the game like the downloadable molten core game (not on the 2600 sadly) and the now playable race, the pandaren.