VIDEO: Un-Aired Footage - Barbra Streisand/Alec Baldwin TONIGHT SHOW Duet Goes Off the Rails

Back in August, Barbra Streisand and Alec Baldwin stopped by THE TONIGHT SHOW on NBC to perform a duet of Stephen Sondheim's "The Best Thing That Ever Has Happened," from Streisand's latest album, ENCORE: Movie Partners Sing Broadway. On last night's show, Jimmy Fallon surprised his guest, Alec Baldwin, with unaiRed Footage from that previous appearance in which he and Streisand end up breaking into laughter. Check it out below!

Barbra Streisand's "Encore: Movie Partners Sing Broadway" is up for a Grammy Award for Best Traditional Pop Vocal Album on Sunday night. 'Encore', which features duets of songs from some of the most beloved Broadway musicals, is the thirty-fifth studio album by Streisand, and was released on August 26, 2016 by Columbia Records. The album features duets with international movie starsHugh Jackman, Jamie Foxx, Chris Pine, Alec Baldwin, Antonio Banderas, Seth MacFarlane,Anne Hathaway and more.

Below, watch the Streisand/Baldwin duet of the Sondheim classic: