This pet is rewarded at the completion of a small questline:
The introductory quest is A Season for Celebration (Alliance) or A Season for Celebration (Horde).
The introductory quest then leads to A Friend in Need (Alliance) (offered by Gretchen Fenlow) or A Friend in Need (Horde) (offered by Candace Fenlow).
Anson Hastings offers Missing Heirlooms to Alliance players. Edgar Goodwind offers Missing Heirlooms to Horde players.
The dead Alliance courier offers Fencing the Goods (Alliance). The dead Horde courier offers Fencing the Goods (Horde).
Auctioner Fitch offers Shopping Around to Alliance players. Auctioneer Drezmit offers Shopping Around to Horde players.
Hudson Barnes offers Taking Precautions andto Alliance players. Delian Sunshade offers Taking Precautions to Horde players.
Hudson Barnes then offers The Collector's Agent to Alliance Players. Delian Sunshade then offers The Collector's Agent to Horde players.
Alliance players are given the quest What Now?. Horde players are given the quest What Now?.
Once What Now? is completed, you are awarded the companion pet.