Update: The pet has been discovered!
Apparently there is a special hunter pet coming in patch 6.2 that no one has discovered yet! Petopia, in partnership with Warcraftmounts.com, is currently running a contest on their forums for hunters to discover this new pet on the PTR.
Whoever discovers it and is the first to post screenshots and details for where they tamed it will win a TCG mount, the Corrupted Hippogryph!
Mania from Petopia had the following to say:
<tap tap tap>
Is this thing on? Yeah? … Excellent.
So … I learned something fascinating the other day. You guys have missed something – something veeeery interesting. See, there’s a certain tameable beast with a cool new look on the 6.2 PTR that nobody has reported yet.
Now we could tell you what it is and how to tame it … but we aren’t going to. Instead, we’re going to run a little contest with Petopia’s sister site, Warcraft Mounts, sponsoring the prize. The first person to find this new tameable on the 6.2 PTR and report back with all the necessary details on how to tame it, here on this thread, will win a Corrupted Hippogryph loot code, from the good people at WootLoots.
So here’s what you need to do: First, go find the beast! We’re not going to give you any hints about this creature other than it’s new to patch 6.2, it’s not a look that has been tameable before, and it’s not a simple ‘see beast, tame beast’ kind of tame. Next, get some screenshots! Post a full screenshot of you with the tamed beast on this thread, including your PTR character name and PTR realm (in the unlikely event there’s a dispute and we need to get in touch with you on the PTR realm to verify the tame). Also keep in mind that in order to be eligible for the prize, you must also have an active WoW account on an EU or US server (including Oceanic and Latin America), so we can give it to you.
It’s possible that someone on some other site will report the tame before one of us Petopians does. In that case, we’ll have to declare the contest void and save the loot code for another day. Let’s avoid that, though, by beating them to it. So go forth. minions, and tame!
As you can see, there’s no hints at all. Is it in Tanaan? Is it a rare? Is it a challenge tame? Is it an existing beast that was previously untameable? If you find and successfully tame the pet, you need to be a registered member of the Petopia forums and post your find in this thread in order to win the mount.
It’s not one of the beasts featured on the front page of Petopia, or the new Diresnout Felboar (not on their site as of now).