We all hate this day on the web. Except for what Blizzard pulls out of their hats. They have a deep understanding of what 4-1 should be on the internet: A very ironic, very funny, and very awesome day. They did it again with this Diablo III class announcement, and this Starcraft II announcement. Make sure you watch the little videos on each of those pages. They are genius.
EDIT: This just in, the WoW Battle Dance system.