Among the data mined from patch 5.3 is a potential new addition to the Darkmoon Faire: a new boss. In the current PTR build, the boss's name seems to be Moonfang. In the full version of the picture above (which can be found on MMO-Champion), you can see a crescent moon that floats above Moonfang's head.
Chances are good this new dire wolf will work similarly to the Darkmoon Rabbit added back in patch 5.0.4, which is a ferocious world boss despite its unassuming appearance. Like the Darkmoon Rabbit, this new dire wolf boss appears to drop a battle pet: Moon Moon.
In addition to the battle pet, Moonfang will also drop Moonfang's Paw. Moonfang's Paw is a statless vanity fist weapon to be used in transmogrification.