Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily. Something strange is happening in yarn stores across the U.S. Eat Sleep Knit, a yarn store in Dallas, Georgia, posted a photo on Tuesday of plastic tubs overflowing with skeins of scarlet and crimson and magenta—all from orders it had received over the past few days. Other yarn stores, like Starlight Knitting Society, in Portland, Oregon, posted assurances for worried customers: Yes, we have red yarn. But Needle and Skein, the yarn store in St. Louis Park, Minnesota, that...