This event may be called the International Children’s Games, but these kids aren’t playing around. The 1,500 athletes, ranging in age from 12 to 15 and representing 50 countries, are hardcore. Playing against the somewhat limiting squeaky clean image of the games, ad agency Grey San Francisco came up with a campiagn that makes kids look a bit more...hmm...fierce. The kids ate it up. Free haircuts and henna tattoos were given to all who wanted them, turning hundreds of kids into walking billboards—nothing wrong with a bit of kid-powered viral marketing.