When it debuted: 1982
Segment lowlight: The trick that started it all.
At its best, late-night comedy can provide penetrating cultural commentary on topical issues that is too edgy for prime-time. At its worst, late-night schtick devolves into America's Funniest Home Videos. Letterman's "Stupid Pet Tricks," which is exactly what it sounds like, is the Ironman of stupid late-night gags.
The joke is even older than Letterman's desk, as the segment originally appeared on the morning show he hosted before he moved to late night. Animal gags have been a stand-by for Letterman ever since, usually garnering uproarious audience applause...which shakes our faith in humanity.
(But let's be real: We're not entirely opposed to low-brow animal jokes on TV.)