Las Vegas-based alternative rock outfit Panic! At The Disco reunited to headline the When We Were Young music festival Oct. 18 and 19. The band celebrated the 20th anniversary of their first album, “A Fever You Can’t Sweat Out,” by playing the album in its entirety.

In January 2024, frontman Brendon Urie announced that the band would be breaking up to focus on his family, as he and his wife were expecting their first child. The When We Were Young music festival announced that the band would be headlining next year after concluding their final tour in March. Due to high demand, the festival added a second day. It was a true surprise to fans to see the band reunite so soon after parting ways.

Following performances from icons like Blink-182 and Avril Lavigne, Panic! At The Disco lit up the main stage, performing some songs that have not been sung live in a decade. The band honored the vaudeville-circus aesthetic of their first album with a captivatingly flashy set design. The band put on an electrifying show, continuing the set with some of their hits, like “High Hopes” and “Victorious.”

The highlight of the night was when the band brought out founding member Spencer Smith to join them on the drums to close the show with a performance of their breakthrough hit, “I Write Sins Not Tragedies.” “This whole thing was started with this one song,” Urie said, “and I wanna bring my oldest friend out on stage, we’re gonna play it.” After finishing the performance, the band and Smith took a bow together. Urie and Smith shared a hug before leaving the stage.

Fans had speculated whether or not Urie, the only remaining founding member, would bring out any of his former bandmates to perform with him. This was further fueled by reports of founding member Ryan Ross being spotted in Vegas, as well as a cryptic Instagram post from Smith, referencing a line from their song “Build God, Then We’ll Talk.”

Concertgoers were given exclusive “room keys” with a QR code that sent them to a hidden website riddled with references to lyrics and music videos from the band’s first album. The website also included an unreleased demo version of “I Write Sins Not Tragedies.” The website hinted at an announcement on Monday, Oct. 19.

The band then announced a 20th anniversary box set and new merch. They also released a live album from their iconic “Live in Denver” concert. Panic! At The Disco’s performance at the When We Were Young music festival was more than a performance for the band; it was a chance for the band and fans alike to celebrate the album that started it all.