Feline Familiar
Source: World Event. Ride with the moon (and this furry, whiskered witch) in the dead of night! Beast type. It is a lot of fun running this trio for PvP: Mr. Bigglesworth Fluxfire Feline Feline Familiar MEOW
The 
Feline Familiar is a World Event battle pet obtained during Hallow's End.
Guide awaiting review
Obtain the Feline Familiar
The Feline Familiar is a Hallow's End World Event pet. Check the Auction House if you are unable to obtain it during the event, as it is tradeable between players.
Level It in Valley
Use Pounce, Stoneskin, and Devour in the Valley of the Four Winds to level efficiently — Stoneskin absorbs damage and Devour restores health, especially against critters, letting the Feline Familiar solo most battles without visiting the stable master.
Upgrade to Rare Quality
Upgrading your Feline Familiar to Rare quality is recommended since it has low base health, making the extra stats a meaningful improvement for battle durability.
Use Onyx Bite in PvP
Onyx Bite is a Magic-type attack that deals extra damage against Flying-type pets, turning what would otherwise be a weakness for a cat into a strength — pairing it with Devour for self-healing makes it a strong PvP pick alongside pets like Mr. Bigglesworth and Fluxfire Feline.
Tips
When power leveling in the Valley of the Four Winds, bring two lower-level pets along since the Feline Familiar can solo encounters on its own — consider adding a Darkmoon Zeppelin or Mechanical Pandaren Dragonling if you need a pet that can shield very low level companions.
For a full video walkthrough, see the video guide linked above.
