Developer Jeremy Feasel pointed out on Twitter that Graves responds to not only /dance, but also /cheer, /talk, and /roar. Tried it out in-game and I feel bad for roaring at him because he ends up cowering. :( Still cute though :)
After a day of waiting (and some worrying), I finally received Graves! Wheee!
I logged into Heroes early this morning and was prompted with a notification that I had earned Graves (and the Hearthstone card back), so of course I had to log immediately into WoW and collect my little golem.
He may not have been able to help in the battle in Heroes, but he can come help me in Pet Battles instead! In just a few stone tosses (ok, maybe 24) Graves was quickly level 25. :)
Graves has some interesting animations. He idles about and also occasionally sits down. If you emote /dance at him, he'll do a cute little dance on his tiptoes (pictured above).
Additionally, he'll cast his signature telegraphed stun move and then stomp the ground (pictured below). If you've played Heroes before, you'll recognize this is the same move that Graves' larger counterpart does down in the mines on the Haunted Mines map.
It doesn't actually do any damage or stun, though. How neat would it have been if it had a daze/stun effect (but not an actual stun) like when Nuts throws acorns at you? Would have been really appropriate. :)
Overall, I'm pretty please with Graves. I haven't tried him in Pet Battles yet, but I hear he's decent. I don't know if he's an OP "must have" like a few other promotion pets though.
Regardless, I'd still recommend collecting Graves. It took some grinding in a game genre that I wasn't familiar or comfortable with, but it was worth it. He's got neat idle animations AND player interaction. Plus his flavor text and background gives me the feels in my heart-space...even if he's not the prettiest pet. :P
Blizzard is slowly working on sending out this pet to everyone (those eligible should have it by the end of the week), so check your Heroes account every now and then for the achievement prompt.
Good luck to everyone still working towards collecting Graves!