How much has Pet Battles changed since the first time it was inadvertently released? The UI has improved tremendously. Mechanics, animations, and the whole works are much smoother.
So how does one get started? First things first. Your character needs to gain the ability to engage mini-pets out in the world. In order to that, you'll need to find your local battle pet trainer. In my case, I booked it straight to Stormwind and asked a guard where the nearest trainer was. You'll find Audrey Burnhep just northeast of the Dwarven District next to the Eastern Earthshrine where all the Cataclysm portal zones are. I ended up forking over 80 pieces of my hard-earned gold to earn the right to use my pets. (Note: This was with the faction discount, otherwise it's 100g.)
Filed under: Mists of Pandaria