El Pollo Grande

El Pollo Grande is a huge black level 50 chicken summoned by Niby the Almighty in Felwood. It is classified as a beast and is not tameable. It has no loot.

Niby summons this ferocious fowl when you turn in the quest. It was not his intention to summon a demonic chicken, but rather something that he could use to extract his revenge on Stormwind City.

As a mount
There is also a WoW TCG loot card in the Fields of Honor set, called El Pollo Grande, which can be redeemed for a giant chicken mount.