Chappelle and Letterman, who had a Chappelle-branded face mask hanging off his ear, were followed by a big camera crew -- which seems to indicate they're shooting an episode of Letterman's interview show, "My Next Guest Needs No Introduction."
However, Chappelle's been doing socially-distanced comedy -- which he's dubbed 'Chappelle Summer Camp' -- and Letterman popped up there too. It's unclear if Letterman actually did a little standup.
Chris Rock's already flown in for one of Chappelle's shows, which have featured Jon Stewart, Jon Hamm,Tiffany Haddish, Michael Che, Erykah Badu, Common, Donnell Rawlings, Talib Kweli and Michelle Wolf.
In any event, whatever Chappelle and Letterman are cooking up, it's sure to be funny!!!