In a spoof of the romantic ballad "Tonight" from "West Side Story," Leno, who was backstage at the "Tonight" show on the West Coast, and Fallon, in his "Late Night" office in Manhattan, serenaded each other by cellphone.
Fallon plaintively asked Leno if they're still friends, despite reports that Fallon will soon displace Leno as "Tonight" host. Leno assured him they are.
Then the number began, with the duo warbling, "Tonight, tonight, who's gonna host 'Tonight'? ... Why do they say we fight?"
And the big finish: "Tonight, tonight, who cares who hosts 'Tonight'? People just watch online the next day!"
Check out the video.