It will be the first appearance on David Letterman’s late-night show in 13 years for Conan O’Brien when he hits the chair next Thursday (May 17). The now-TBS late-night host replaced Letterman as host of NBC’s Late Night in 1993 after Letterman left for CBS. Of course, O’Brien eventually (and briefly) was host of The Tonight Show, a gig Letterman wanted back in the day and led to his departure from NBC after the job went to Jay Leno.