As I'm sure you know, worgen are classified as a humanoid. However, one wolf in Howling Fjord, Garwal, is a wolf that turns into a worgen at ~55%. Also, you need the quest Alpha Worg to see him.
If you tame Garwal as he is turning into a worgen, or a little bit beforehand, he will transform into a worgen as you tame him, keeping his worgen form.
Garwal will stay this way as long as you have him. Happy hunting!
Edit: Worgen Pet. This is not me in the pic, btw, it is someone else who has the worgen pet.
1. Get Wyvern Sting. It does about 19% damage by itself over 6 secs, and sleeps for 30.
2. Find him.
3. Hurt him until he is approx 67-69% health.
4. Wyvern sting him.
5. Wait till there is 14 secs left on Wyvern sting.
6. At 14 secs left, cast tame beast.
7. If done right, right as your tame ends, he will have just transformed.
Posted on forum.
World of Warcraft - English (NA) Forums -> Worgen pet?
Pics are also in there.
I just tamed him, he keeps his worgen form through logout, dismiss, etc.
I hope Blizz will let us keep it after fix.
Your taming must finish just after he says "enough of this disgui.se" or sth similar. (at 49%)
few more advices.
1.DONT RELY on the guide posted, just use your brain and try to perfect your timing
2. you can also wyvern sting him JUST when he says "Enough of this charade!', if you'll do it correct, then he'll still be in wolf form, sleeping, at 20sec, use tame beast, that do not works all the time tho.
I've spent over 1:30hour, trying to figure out the best way for lvl 73 to get it. Wyvern Sting on 51%, and tame beast at 13 sec worked for me.
And believe me ... ITS WORTH to spend a lot of time to get it. That ssimply most amazin pet in-game EVER.