Blizzard tends to have some good april fool's jokes, some of which became popular enough to survive being solely a joke, like when they announced the Panderans as the 4th race for Warcraft 3 on April 1st, but everyone liked them so they ended up making it into the franchises lore after all.
I loved their page about the new Bard hero class in Wrath of the Lich King this year, complete with a Guitar Hero style fret board going up half the screen.