This is Hallmark country, which is all well and good when it's time to send Grandma a card or buy Junior a teddy bear. But the king of card sellers leaves those of us who appreciate a good dirty joke woefully underserved. Enter Ted and Cindy Larkin, unabashed purveyors of silly smut at Twisted Sister, a little sliver of a shop on a well-trafficked block of West 39th Street. For nine years, the Larkins' register has sung out with sales of greeting cards and novelties. It's easy to leave stocked with enough birthday cards to send to friends you haven't even made yet. Some are perfectly suitable to offer your neighbor or your boss, but some must be limited to the closest of friends, and still others would make a drag queen blush. The Larkins definitely have found their niche. After all, when was the last time you saved an e-card?