Blue Murloc Egg

The Blue Murloc Egg item teaches you to summon Murky, a blue baby murloc Companion that follows you around.

Source
During BlizzCon 2005, cards with special codes were given out to attendees to obtain the Blue Murloc Egg in-game. This pet is only available to them, and the code is redeemable only once.

How to obtain: (Alliance)
 * To obtain Murky, head to The Forlorn Cavern section in Ironforge in the dwarven area, Dun Morogh.
 * Head to the shore of the pond where Ransin Donner, a dwarf stands with Murky, the blue baby murloc small pet.
 * Talk to him to enter your code.

How to obtain: (Horde)
 * To obtain Murky, head to the Valley of Honor section in Orgrimmar in the orcish land of Durotar.
 * You'll see a dock in a small pond where Zas'Tysh, an orc, stands with Murky, the blue baby murloc small pet.
 * Talk to him to enter your code.

Pet Journal
Appearances of this beloved and ultra-reclusive murloc are sure to draw a crowd.

Official Description

 * Many would say that the Murlocs are filthy, slimy creatures with no greater purpose in life than to serve as expendable sparring partners for aspiring heroes. Do you believe this? Think again! Mindless killings and raids on their homes have left thousands upon thousands of Murlocs dead or wounded, and each day the slaughter continues.


 * Have you ever invaded a Murloc settlement and drenched your blade in their green blood? Have you ever ended the life of one of these poor, defenseless creatures as it was desperately trying to escape back into the safety of a nearby river or the sea, the Murloc's true home? Yes? Then it is time you made up for the pain and suffering you have caused these gentle animals!


 * Through the Murloc adoption program you will have a chance to get to know these fascinating and playful creatures from a whole new perspective. Many young Murlocs are left without their parents as pillaging gangs of so-called heroes eradicate entire tribes, leaving the unhatched Murloc eggs without protection against hungry crocolisks, raptors, and other dangers that threaten a young Murloc's life. Many kind souls have saved abandoned eggs from ravaged Murloc settlements, and you can help us hatch these eggs and care for your very own baby Murloc. If you have been given a special code that certifies you as a qualified Murloc handler, please follow the instructions below to turn in your code and to receive your new best friend in the World of Warcraft.

Expiration
On September, 12th 2006 it was announced on the US forums that BlizzCon gift cards which were given on BlizzCon 2005 were going to expire on October, 28th 2006 at 12:01 AM PDT, though after many requests it was announced that all the murloc codes will be still active till further announcement and only the beta keys have been expired on October, 28th 2006.

In dialog, both Ransin Donner and Zas'Tysh both still offer to redeem the code for Murky.