As one of those people, specifically the one swaying gently with the gryphon plushy, I can give you a little bit of background! Blizzard sent out an email a couple of weeks back, asking for people to create a video of themselves singing along to the chorus. There were no other stipulations, and, as Blizzard had no control whatsoever over the finished product, there were no guarantees that your clip would be included. And, of course, we had to keep it under our hats. Luckily, they didn't use our audio. Hope you like it, I was honored to be included!