Did You Know?
The fight between Andy Kaufman
and Jerry Lawler
was staged. The original plan was to have the two apologize to each other and then for Kaufman to sing "What the World Needs Now (Is Love, Sweet Love)". But according to Lawler, sometime before the taping, Kaufman asked him to slap him instead. After some coaxing, Lawler decided to go along with the idea. Since Letterman was expecting the apology shtick, he was genuinely bewildered when the fight broke out. See more
Referenced in My Breakfast with Blassie