“We had a bad show … The guests were bad, and I was feeling pretty bad about myself at the end of the program,” Kimmel told NPR in 2013. “And I decided to say, for the amusement of one of our producers who was standing next to me … ‘I want to apologize to Matt Damon. We ran out of time.’ … And he got a kick out of it, the producer, so I just started doing it every night to amuse him.”
And even though he only said Damon’s name because it’s the first A-lister he thought of, the joke stuck after the December 2005 episode. The host then spent about a year closing his show with the same apology to Damon before the actor himself came on to participate in a fake fight in 2006 after he finally makes it on the show and the host cuts him off.