Massively: "We've got a hot tip directly from WoW Insider for you this morning. If you've got a currently active World of Warcraft account, and there's any way at all you can spare the time tomorrow to log in, do it! Tomorrow is WoW's fourth birthday, and Blizzard is handing out some presents for all the players logging in on this auspicious occasion! Simply logging your character into World of Warcraft tomorrow will net you an achievement and an in-game pet. The pet is the cutie-patootie shown above, a "Baby Blizzard Bear".
The achievement is a one-of-a-kind can't-get-it-any-other-way feat of strength achievement. Other achievements handed out for this include other date-based events, things players will never be able to get again."