Nero's pet, Kog'maw was the sole survivor of his litter.

The party grabbed a few eggs from a cave near the border of The Empire in the Horde's lands, after slaying their mother.

Only one survived the trip back to The Empire, and it was given to Abathur for him to hatch. Eventually Kog'maw was delivered to Nero with his petrifying gaze ability removed, but adorableness intact.