You need to get the zoomies for more than 20 seconds while disguised as a pet. Because you need to be disguised as a pet, you'll pick up the Pet Mischief achievement in the process.

Getting to Siren Isle in World of Warcraft can be tricky. Filled with speeding cars and black-blood crazed workers, you must explore the Undermine to stop Chrome King Gallywix in his tracks.