In the U.K., around half of all 6- to 11-year-olds have joined a social-networking site called Moshi Monsters. Owned by London’s Mind Candy, it’s a virtual world where kids can nurture their monsters—avatars that look like Care Bears—by decorating their virtual rooms with furniture, paintings, and notes. The characters have spilled out into newsstands and toy stores. The bestselling magazine for children in Britain is, of course, Moshi Monsters Magazine, and the only toy brand that outsells Moshi stuffed animals is Lego. Moshi’s biggest market, however, is now the U.S., where more than one quarter of its 50 million members live. Mind Candy’s founder, Michael Acton Smith, says more than half a billion messages have been sent between users since the site launched in April 2008.