Note to self – comedians play jokes. That’s why David Letterman walked out on his interview with Joan Rivers last night. 

According to Showbiz 411, Rivers was on “The Late Show” to promote her latest book, “Diary of a Mad Diva” when she and Dave decided to pull the prank. You’ll recall that Joan walked out of a CNN interview over the weekend. 

CBS released an official clip that everyone picked up…and thought was real. Again I say unto you…comedians play jokes. 

Source: Showbiz 411