A lot of readers tipped this in while looking through Wowhead's comprehensive Achievements database. While we've actually heard of rumors of the Wrath of the Lich King Collector's Edition, with pictures of the box supposedly making their way out of the printers, this Achievement more or less confirms that there will be a Collector's Edition and that the Frost Wyrm whelp model leaked in Alpha is actually the Collector's Edition pet.
The Achievement falls under Feats of Strength, along with the other Collector's Edition Achievements The requirement is possession of Frosty's Collar, an item not yet implemented in Beta. The Achievements page defines the Feats of Strength as "an accomplishment that players will find either very difficult if not impossible to earn. Feats of Strength are a collection of past glories on Azeroth."