Fairly simple one this. Once you get to The Meat level, you'll come to a walkway where you must cross with your orb, whilst these huge pimples will grow all over the walkway attempting to push the orb off the sides. I managed to get this achievement within about a minute by sitting my orb near the middle of the walkway and running each of my characters across as many growing pimples as I could reach within the orb's light radius.
Remember and keep an eye for any pimples growing near the orb incase it pushes it off the side! I tended to keep one character pretty close to the orb to keep it safe.