Lurky's Egg



The Lurky's Egg item summons and dismisses Lurky, a white baby murloc Companion. Due to Lurky's pale color he might be a baby Blindlight murloc similar to those in Blackfathom Depths or a relative of the Wailing Caverns boss Mutanus the Devourer.

Source
This item is available only to European players who bought the Collector's Edition of the Burning Crusade expansion pack, where they were given as compensation for a mistake with the Nether Whelp pets.

Unlike the pets from the Collector's Edition of World of Warcraft, the Lurky's Egg item is attached and sent to all your characters, present and future, in the mail as soon as upgrade your account. You must retrieve Lucky's Egg from the mail within 30 days of upgrading (for existing characters) or character creation (for new characters) for each character, or that character's Lurky's Egg is lost.

Blizzard has announced that once you upgrade your game, you cannot re-upgrade it with a Collector's Edition at a later time. This means that the characters associated with your regularly upgraded account can never obtain this item. Transferring a character to a Collector's Edition account will not allow that character to obtain this item. 

However due to numerous requests, Blizzard officially announced on January 22, 2007 that they are working on a solution to help customers re-upgrade their accounts. Those who fall in this category are asked to contact their Billing and Account Services department. Those who posted in the thread at the WoW forum have mentioned their having been able to get their accounts manually re-upgraded using this method. 

BtA issue
Unlike the Netherwhelp's Collar, which was made BtA in Patch 3.0.2, this pet did not get the same treatment until Patch 3.0.3.