DIY these 'Cosby sweater' leggings! If you don't know what a Cosby sweater is, well that is another story entirely. Basically, thrift an old sweater; steal one from Grandpa's closet or buy an expensive Cynthia Rowley. Cut arms off and sew to a pair of leggings that have been cut above the knees and wa'lah insta fashionista!