Catherine Moellering, head of trend-spotting firm Tobe, traces the roots of the pajama look back more than a decade, to a time when Juicy Couture velour tracksuits were the rage.
Ms. Moellering points to the influence of celebrities like Kim Kardashian, Britney Spears and Miley Cyrus, who are photographed at one end of the spectrum or the other either dressed way down when trying to dodge the paparazzi, or all dolled up for the red carpet.