This might be old news to some people, but thought I would share for people who may not know about it and who are going for the pet achievements.
Mountain Dew is doing a promotion for their WoW related drink stuff. If you go to
http://www.mountaindewgamefuel.com/ and click the button on the bottom right that says "Battle Bot Pet, Claim Now & Fuel Up" it will direct you to the battlenet site to log in. If you have not merged your account with Battlenet then this will not work. You would have to do that first.
You do NOT have to sign up for Mountain Dew's website. Just log in with your battlenet account and it will give you a message that its sent you the pet. These pets will battle other pets using opposing fuel colors. You can only get fuel once per day using the stupid website link, so thats annoying, but you get a free pet out of the deal.
It took about 30 minutes for my pet to be delivered after logging fully out of the game and back in. The pet itself looks exactly like the clockwork robot, with the exceptions that it has two tanks on its back for fuel and is silver. They're kind of neat but only worth the trouble if you are into pet collecting.
OH and FYI once it sends you the pet, it will go to the mailbox for every one of your characters on every realm you play on. I checked.
WoWHead link to Battlebot ]http://www.wowhead.com/?spell=65682