Seeing double. Mary-Kate and Ashley Olsen were spotted on a rare joint outing in New York City on Tuesday. In photos obtained by Page Six, the twins dressed casually, with Mary-Kate wearing baggy, knee-length black shorts paired with a white T-shirt, a black scarf, black shades and vintage sneakers from a Yohji Yamamoto x Adidas 2002 collaboration. She wore her dirty blond hair in waves and carried an oversized brown snakeskin bag. Meanwhile, Ashley wore an all-black ensemble, consisting of a sweater, jeans, sandals and sunglasses. She also wore her hair down and completed her look with black sunglasses and a black Margaux bag from their…