Treat Bag

Treat Bags are given out by the innkeepers in Azeroth and Outland during the Hallow's End festival seasonal event. It contains random loot from the Hallow's End seasonal event.

Source
Once per hour, you can talk to an innkeeper and select the dialog option, Trick or Treat!. The innkeeper will either give you a Treat Bag or a Trick, temporarily polymorphing your character. The Treat Bag should be opened and looted once you get it, as it will disappear if you log out of the game.

After you speak to an innkeeper for a Treat Bag, you will receive a 60 minute debuff which will prevent you from getting more Treat Bags until the debuff expires. You must make sure you have an empty bag slot for a treat bag since you will still get the debuff from the innkeeper regardless of whether the treat bag is able to fit into your bags or not.

Contains
The Treat Bag randomly contains any of these prizes:
 * Sinister Squashling ?%
 * Hallowed Helm ?%
 * 10 2%?
 * Penny Pouch 2%?
 * 4-6 13-65.8%
 * 4-6 Candy Corn 14-65.6%
 * 4-6 13-66%
 * Hallowed Wand - Bat 2.1-2.3%
 * Hallowed Wand - Ghost 2.1-2.3%
 * Hallowed Wand - Leper Gnome 2.1-2.3%
 * Hallowed Wand - Ninja 2.1-2.3%
 * Hallowed Wand - Pirate 2.1-2.3%
 * Hallowed Wand - Random 14.7-15%
 * Hallowed Wand - Skeleton 2.1-2.3%
 * Hallowed Wand - Wisp 2.1-2.3%
 * Flimsy Female Blood Elf Mask ?%
 * Flimsy Female Draenei Mask ?%
 * Flimsy Female Dwarf Mask 1.8-2%
 * Flimsy Female Gnome Mask 1.8-2%
 * Flimsy Female Human Mask 1.8-2%
 * Flimsy Female Night Elf Mask 1.8-2%
 * Flimsy Female Orc Mask 1.8-2%
 * Flimsy Female Tauren Mask 1.8-2%
 * Flimsy Female Troll Mask 1.8-2%
 * Flimsy Female Undead Mask 1.8-2%
 * Flimsy Male Blood Elf Mask ?%
 * Flimsy Male Draenei Mask ?%
 * Flimsy Male Dwarf Mask 1.8-2%
 * Flimsy Male Gnome Mask 1.8-2%
 * Flimsy Male Human Mask 1.8-2%
 * Flimsy Male Night Elf Mask 1.8-2%
 * Flimsy Male Orc Mask 1.8-2%
 * Flimsy Male Tauren Mask 1.8-2%
 * Flimsy Male Troll Mask 1.8-2%
 * Flimsy Male Undead Mask 1.8-2%