Justin Timberlake, Jimmy Fallon collaborate for song on Fallon's holiday album

Oct. 14 (UPI) -- Jimmy Fallon has an upcoming Christmas album, called Holiday Seasoning , featuring a collaboration with Justin Timberlake .

The Tonight Show host shared his new project during an interview on Watch What Happens: Live .

"I wrote every one of the songs," Fallon told Andy Cohen . "I wrote 16 originals -- 16 fit on the vinyl -- and then the deluxe, the digital, comes with another six songs, maybe 23 songs total, something like that."

Timberlake joins Fallon for "You'll be There," a song about a "bromance" where one friend pines for the other's attention during the holidays.

Fallon also promoted a children's book, Cohen shared, called 5 More Sleeps 'Til Halloween .

"You are so prolific. I am blown away by your creativity," Cohen tells Fallon. "And you said on the show that you wake up and you record ideas. This guy, if you go to dinner with him, he will pull out his notes app, and just go through ideas that he has. He has the best ideas."

One such idea was the song that ultimately became the tight pants gag with Will Ferrell .

"That came to me in a dream," Fallon said. "...It's me and Will Ferrell wearing tight white pants, and we want to see who has the tightest pants in the land."

Fallon also hinted at a "big fun thing" in the works for SNL's 50th anniversary.

Holiday Seasoning drops Nov. 1.