The Supervillain Twins are a pair of thirteen-year-old identical twin sisters named Milly and Tilly. Milly's supervillain name is 'Sneaky Swimmer', and she has the power to breathe underwater and camouflage herself underwater as well. Tilly's supervillain name is 'Frightening Fairy', and she has the power to fly, as well as making any scary monster appear with a wave of her 'Monster Wand'. Both twins always wear long-sleeved full-body rubber jumpsuits, rubber gloves, utility belts and swimming goggles. Milly also wears a swimming cap, a pair of flippers, a superhero cape, a pair of nose-clips and a scuba breather that holds infinite air, while Tilly also has a pair of fairy wings strapped to her back and wears a pair of boots and a tutu. Tilly keeps a variety of wands in her utility belt, each for different purposes. The twins only have one main goal: to take over the world!