This NBC Christmas special featured Jimmy Fallon and his celebrity friends spicing up the season with performances from his festive holiday album, “Holiday Seasoning.” The star-studded lineup of guests includes Meghan Trainor, Cara Delevingne, Dolly Parton, Jonas Brothers, JB Smoove, Justin Timberlake, LL Cool J, The Roots, Weird Al Yankovic, and more.