Primates: WoW Battle Pets
Select a pet:

World Event: Darkmoon Faire (first week of each month)
Vendor: Lhara
Zone: Darkmoon Island
Cost: 90 (unlimited supply)
Drop: Darkmoon Game Prize
Zone: Darkmoon Island
Approximate Drop Rate: 1 in 1,250

TIP: The Guide to Pet Collecting is a great place to start for the novice pet collector.