Recruit-A-Friend Pet Rewards
Blizzard made an announcement that the Recruit-A-Friend program would be receiving a revamp in the near future. Part of the update may include redeemable pets!
The PTR Pet Journal currently lists four RAF pets. Originally, these pets were only available for a limited time in Asian regions. All of them are unique and non-tradeable.
There are other Asia-exclusive companions, however they have not been updated to "RAF status" at this time. It's possible that they may join the ranks of RAF pets in the future.
We'll have to wait and see how the new RAF program works, and what will be required to redeem these pets.
One thing seems likely though, more friends that join you in Azeroth may mean more pets for your collection!