The duet, which aired on Monday's edition of Fallon's "Late Night," takes aim at the media speculation regarding Leno's much talked about, but-as-yet-unannounced retirement from "Tonight" next year and Fallon's apparent taking his place.
The video shows Fallon and Leno talking on the phone about the situation and agreeing they are "still friends" as they are hounded to comment on the rumors.
"In the news, all they do, is say I'm replacing you. They think I can woo the demo," Fallon sings.
"So the network says here's an idea, pack your bags, take a hike, NBC-ya," Leno replies.
"Tonight, tonight. Who's gonna host 'Tonight?' Is it gonna be Jimmy or Jay," Fallon adds. "Tonight, tonight. Where will they tape 'Tonight?' In New York? Or will it stay in L.A.?"
"Tonight, tonight. My ratings were all right; 20 years and I'm still in first place," Leno croons back. "Tonight, tonight. I've got Fox on the line, or maybe I could take over for Dave."