Popular culture moves fast these days. All it takes is one appearance on MTV's Total Request Live to turn something cutting-edge into a mass-produced fad. Witness the mod revival, brought on by the success of New York City phenomenon the Strokes. Everywhere now are scruffy-haired boys in size-zero slacks and little girls wearing pencil-thin ties. Meanwhile, the world's true fashionistas are looking further back in time for inspiration -- to the court of King Arthur. In recent weeks, we've spotted two chain-mail headdresses in the midtown area. One guy wore his with a baggy white T-shirt and black cotton shorts, and he still pulled it off like some kind of male Cher. It may be a few years before this really catches on, but expect to see a chain-mail headdress on the cover of Rolling Stone before the decade is out.