During the Jonas Brothers' second concert on their “Five Albums. One Night.” tour, Jimmy Fallon surprised fans by appearing on stage with the band.

While on stage, Fallon led a sing-along with the crowd of The Killers' song, “Mr. Brightside.”

“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,” Fallon said in a tweet with a video attached.

In a follow-up tweet, Fallon also thanked The Killers: “And thank you to @thekillers for writing a JAM #MrBrightside.”

The “Five Albums. One Night.” tour — also known simply as “The Tour” — is the Jonas Brothers' latest world tour. It's in support of their sixth studio album, The Album, which dropped on May 12. “The Tour” marks the twelfth concert tour from the Jonas Brothers of their career. They're coming off of the “Remember This” tour that ran from 2021-2022.

“The Tour” kicked off with two shows at Yankee Stadium in the Bronx before heading off and hitting all of the major U.S. cities. They also announced international dates that will take them to New Zealand, Australia, Norway, Germany, France, England, Ireland, and more. The tour is set to conclude on June 20, 2024, in Belfast, Northern Ireland, at the SSE Arena.

Jimmy Fallon is no stranger to appear on-stage with some of the world's biggest acts. The Tonight Show host previously appeared on stage with U2 during their 2015 residency at Madison Square Garden to perform “Desire” off Rattle and Hum.