By Bonnie Stiernberg Yesterday marked 40 years since Late Night With David Letterman premiered, and to celebrate the occasion, the now-retired late-night icon (who still turns up occasionally on Netflix’s My Next Guest Needs No Introduction) launched a new YouTube channel full of vintage clips from his time hosting Late Night and The Late Show. As you might expect, it’s a treasure trove of memorable celebrity interviews (like the time Drew Barrymore showed up and flashed Dave for his birthday), goofy recurring segments like Stupid Pet Tricks and the delightfully bizarre man-on-the-street bits …