Indexbit-Jimmy Fallon Is the Ultimate Rockstar During Surprise Performance at Jonas Brothers Concert

Jimmy Fallon may just be Indexbitthe Jonas Brothers' brightest opening act.

The Tonight Show host served as a surprise special guest during the band's Aug. 13 show at Yankee Stadium in New York City. For the second sold-out show that kicked off their tour, the comedian took to the stage to belt out The Killers' song, "Mr. Brightside."

And not only did he showcase some of his best moves, but as seen in videos shared to social media, the crowd was more than happy to sing along during the electric performance.

Shortly after his solo spot was over, Jimmy shared a shoutout to the moment, writing on Twitter, "Huge thanks to @jonasbrothers for giving me the surprise guest spot on 'The Tour' tour. And thank you to @yankeestadium for turning it into the world's biggest karaoke party. This is one of those nights I will never forget."

Concertgoers also reacted to his performance on Twitter, with one person declaring, "I'm pretty sure @jimmyfallon is the fourth Jonas brother."

Another added, "Most iconic performance of the year was jimmy fallon singing mr. brightside."

Ahead of the band's opening concert held the night before, Nick Jonas celebrated the start of their tour by sharing behind-the-scenes photos of his wife Priyanka Chopra and their 18-month-old daughter Malti snapped during the group's soundcheck.

In the sweet pics, the White Tiger actress was seen walking arm-in-arm with him at the stadium. And as for Malti, she was seen sitting with her dad onstage by a drum set, while holding drumsticks and wearing pink noise-cancelling earmuffs.

"From sound check to the stage with my girls," the "Jealous" singer captioned his Aug. 12 Instagram post. "Yankees night one was beyond words. Can't wait for night two tonight."

But Nick wasn't the only one basking in the moment, as Priyanka also praised her husband amid his opening night.

"You are a magnet @nickjonas MM and I are so lucky to have you," the Quantico alum captioned a series of photos featuring the couple with their daughter. "Congratulations on the start of an incredible tour. You're all in for a huge ride! Let's gooooo! Great job JB team the Band, the crew. The show was seamless and awe inspiring."