Worg Carrier

Source
This item drops from Quartermaster Zigris in Blackrock Spire. This pet is unique in that it has two "skins". Use of the carrier displays a black-furred pup or a brown-furred pup at random.

Scout Nisstina has a Worg Pup companion in the Black Market area of the Underbelly.

Prior to patch 4.0.3a, it was a quest reward from Kibler's Exotic Pets (quest).

Pet Journal
Worgs are the favored companions of orcs and are fiercely loyal on the battlefield.