Pink Murloc Egg

The Pink Murlog Egg item teaches you to summon Gurky, a pink baby murloc Companion that follows you around.

Source
The Pink Murloc Egg access code was given as a prize for several European contests over Christmas 2006.

How to obtain: (Alliance)
 * To obtain Gurky, 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 Companion or Garel Redrock, who stands with Gurky, the pink baby murloc.
 * Talk to him to enter your code.

How to obtain: (Horde)
 * To obtain Gurky, 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 Companion.
 * Talk to him to enter your code.

Pet Journal
Gurky is a born performer, though she remains elusive, making public appearances only on the rarest of occasions.

Notes about redeeming your code for Gurky
From Blizzcon 2007 through sometime in the first half of 2008 both Ransin Donner and Zas'Tysh wore a murloc costume.

Currently, in dialog, neither Ransin Donner nor Zas'Tysh offer to redeem the code for Gurky as of June 6, 2008.