Darkmoon Faire Pets
After looking through Wowhead's PTR database, I've noted that none of the Darkmoon pet items have reputation requirements on them. This may change and although there may not be actual text stating the rep necessary, a certain level of reputation may be required to access the vendors for these companions.
Another interesting thing to note: Currently, the Darkmoon Cub, Monkey, and Turtle are of "blue" quality (rare) while the Darkmoon Balloon, Tonk, and Zeppelin are of "white" quality (common).
I found three other balloon companions; Flimsy Darkmoon Balloon, Flimsy Green Balloon, Flimsy Yellow Balloon. The first is an item that shares the same spell ID as the already mentioned Darkmoon Balloon, which is odd since the Darkmoon Balloon is an item in itself already. My guess for the other two balloons is that they will also be available from the Darkmoon Faire, and possibly different colored faire-themed balloons.
Note: ALL Darkmoon Faire pets are Bind on Pick Up at the moment.
I mentioned a while ago that one of the only in-game holidays that had yet to be paired with a vanity pet was the Lunar Festival. Well, patch 4.3 may prove to correct this!
Datamining brings us news of two companions, the Lunar Lantern (Alliance) and the Festival Lantern (Horde). Since both these companion items don't appear to have Bind on Pick Up tags, one can hope that a character will be able to obtain both, regardless of what faction/race they're from!
Bind to B-net
Out of all the new pets, there is only one that will be bound to your Battle.net account which makes this companion stand out. The Fetish Shaman's Spear item will be BoB-net, but where it will come from... I have no idea!
I've been thinking of appropriate "special" upcoming events in which this pet would fit in, but I'm not coming up with anything. Hell, I'm not even sure what a Fetish Shaman is!
Update: Thanks to a few tips from more experienced and knowledgeable Diablo players, the Fetish Shaman is from the Diablo universe so the pet will likely be the CE vanity pet much like the Mini Thor was SC2's CE companion.
And the Rest
Last but not least, the mix and match of new pets that are all Bind on Pick Up but don't really have a specific time and place for them to turn up. At the moment I don't have much to say about these mini-pets.
I predict the Lump of Coal item will turn up during Winter Veil because well... some people just deserve a lump of coal, I guess? But in this case of pet collectors Lumpy isn't a bad thing, so it's not much of a punishment is it! :P
Oh, I must make a special note about the Sea Pony: Breanni of WarcraftPets.com spoke with Ghostcrawler during Blizzcon 2010, and while it was never promised, he did mention that a baby seahorse companion might be in our future. Well, it looks as though GC came through for us and a