OK, some background for those of you who have no idea why this is even funnier than the song itself. Jimmy Kimmel has this long running joke wherein he invites Matt Damon to be on the show and then at the end of the show announces that he's sorry, but they don't have time for Matt to come out. There's a pretty funny clip of Matt Damon storming out and "losing it" one time. (I'll link it later.) Sara Silverman is dating Jimmy Kimmel, so it's kind of a funny "payback" for the running joke.