You know what's great? Seeing a guest embarrass Letterman instead of the other way around, which is exactly what Drew Barrymore did in 1995. That year on his birthday, she spontaneously jumped onto his desk and, with her back facing the audience, flashed her bazongas in his face.
"It's still something I think about and talk about and tell my friends," Letterman told Barrymore during her visit to the show in 2007, a month before his 60th birthday and right after the 32-year-old actress denied his request for a re-enactment of sorts. There's always next year, you creepy old man you.