Two New Hallow's End Pets

Two pets that were datamined in 4.2 have finally made their appearance! The Creepy Crate and Feline Familiar are two new companions that are available during this year's Hallow's End in-game event. [source]

Obtaining the Two New Pets
The Creepy Crate is a reward after completing a short quest chain (starts with Missing Heirlooms) that is obtainable from a NPC located in the Stormwind Trade District Inn and Orgrimmar Valley of Strength Inn. Upon closer inspection at the preview shown on MMO-Champion, this crate truly is creepy (and apparently hungry)!

The Feline Familiar can be purchased from the Hallow's End vendors. This witch hat-wearing, broom-riding kitty will cost 150 Tricky Treats. The treats can be obtained through the pumpkins at friendly inns as well as Hallow's End quests and dailies. Be sure to save up those candies since there are quite a few new treats being sold during this in-game holiday!