Mullen began practicing in the garage of the family home while wearing a comprehensive pads setup, a precaution that was part of the deal with his father, and spent time with his sister's surfer friends, who skateboarded on weekdays. Mullen became obsessed with the skateboard and practiced for many hours on a daily basis. As a child, Mullen slept in boots designed to correct a severe pigeon-toe condition. Despite Mullen's condition, "He had an incredible dexterity with his feet," in the words of Phil Chiocchio, former owner of the Florida skatepark, Sensation Basin.