That time when I was fifteen and wrote a letter to David Letterman and he read it on the air eventually and then I had to wait 33 years to see it again, thanks to a meticulous Youtuber digitizing lots of Dave's classic bits.
I remember there was at least one more letter where they tore up the studio over a washing machine or something made by GE that stole a listener's money, so TECHNICALLY it became a running bit.
