Backstreet Boys Sing 'Manningcast' Remix of Hit Song

Peyton and Eli Manning really are getting "everybody" to help promote their popular "Manningcast" show ... enlisting none other than the Backstreet Boys to remix one of their biggest songs for the two NFL legends ahead of the new season!!

TMZ Sports has obtained a clip of Brian, AJ, Nick, Howie and Kevin giving an a cappella rendition of their mega hit, "Everybody" ... but instead of the famous lyrics we've all belted out over the past 27 years, they swapped them out for some Manningcast-themed lines.

"Everybody (yeeeaaaahhhh), watch the Manningcast (yeeeaaaahhhh)," the boy band legends sang. "Everybody, it's on Monday night ... Manningcast -- ALRIGHT!!"

Pretty freakin' cool!!

We're told Peyton actually crossed paths with BSB at an event earlier ... and the artists all happen to be fans of the "Monday Night Football" broadcast.

So when Omaha Productions reached out to the boys to help out with promo ahead of the 2024-25 campaign, they were totally stoked to get involved.

In fact, we're told BSB didn't even rehearse their "Everybody" remix ... they just counted each other in and killed it. So you could say they're really in sync (ope, wrong group).

Of course, the boys also had a brief cameo in Peyton and Eli's "musical" they released earlier this week ... which also included some major NFL names and huge celebs like Michael Buble, Kevin Hart and Pete Davidson.