'Bachelor' Nick Viall Crashes Backstreet Boys Concert During Epic Group Date

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In perhaps the most epic group date in the ABC show’s history, Bachelor Nick Viall escorted seven ladies to a Backstreet Boys concert at the iHeartRadio Theater in Los Angeles on Friday. <p> And, to make things even more interesting, the 36-year-old joined the boy band during a performance of their hit song “Everybody (Backstreet’s Back).”

EXCLUSIVE: AJ McLean Says Backstreet Boys’ Las Vegas Residency Will Be Their ‘Biggest Show in 24 Years’

Viall was joined on stage by his bachelorettes, who shimmied behind him as back-up dancers.

“Nick looked like he was having a blast,” a witness tells ET. “He kept glancing over to AJ for guidance, but when it came to the chorus he killed it!”

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The GRAMMY-nominated group slowed things down with an acapella version of “I Want It That Way,” while Viall and one lucky lady took center stage for a slow dance.

Singing along, Viall and the brunette cozied up for an intimate dance, which ended in a steamy make-out session.

“The other contestants were in the background dancing along, but some appeared to be bummed it wasn't them dancing with Nick," the witness added.

Before Viall left the stage, the boy band wished him good luck in finding love.

“That was smooth as butter!” McLean exclaimed, after the couple locked lips.

Leena Tailor

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The boy band also hyped up the crowd by bringing former Bachelor contestants, Ashley Iaconetti and Becca Tilley, up to the stage and serenading them with fan favorite, “Get Another Boyfriend,” from their 1999 album Millennium.

Last month, the Backstreet Boys announced their Larger Than Life residency at Planet Hollywood in Las Vegas. For more on their highly anticipated show, see the video below.