VIDEO: Robin Williams Tells Conan O'Brien - "You Got Screwed"

Conan O’Brien packed plenty into his next-to-last evening as host of The Tonight Show Thursday, with another super-expensive bit and a memorable interview with guest Robin Williams.

"You've only been host for seven months," Williams said of O’Brien’s short-lived tenure as host of NBC’s late night franchise. "It's an annulment. Except you got screwed."

Conan O'Brien "Determined To Make Best" Of NBC Departure

Conan O'Brien Signs $44 Million Deal To Leave Tonight Show

Williams serenaded O'Brien with an "Irish ditty," and launched into an obscene song with the lyrics, "F*** NBC," before composing himself with a heartfelt send-off to the lame duck host, calling him "an old Indian word, a mensch." ("Mensch" is actually Yiddish for a person of integrity and honor.)