Plant Life: WoW Battle Pets
Select a pet:
Sinister Squashling — [Sinister Squashling]
World Event: Hallow's End
Item: Crudely Wrapped Gift (obtained via daily Hallow's End quest)
Daily Instance: Headless Horseman [75+]
Drop Rate: 1 in 20 dropped (avg. all sources; available 15 days per year)
TIP: The Guide to Pet Collecting is a great place to start for the novice pet collector.