Weezer's Rivers Cuomo Explains 'Spontaneous' Leighton Meester Duet

Frontman says band was inspired by Hootenanny Tour to work with other artists like Lil Wayne and Katy Perry.

On Saturday night, Weezer celebrated Halloween with a concert at New York's Hammerstein Ballroom. It was your typical Weezer show, full of big hooks and lung-busting sing-alongs, but when it came time for the group to play new single "(If You're Wondering If I Want You To) I Want You To," they welcomed a special guest onstage: "Gossip Girl" star and "Good Girls Go Bad" singer Leighton Meester.

She stormed the stage and duetted with Cuomo on the song, which sounded extremely polished but was mostly off-the-cuff.

"We invited her down, and she was in rehearsal — wait, did she even come to rehearsal? No, she didn't!" Cuomo told MTV News, trying to recollect how the events shook out. "We just worked on it in the dressing room right before the show. 'You sing this line, now I'll sing that line,' just like that. It's best when there's a little rehearsal, so that it can still feel spontaneous."

For most of their 15-year existence, Weezer have pretty much kept to themselves, rarely going outside of their immediate universe. But that has all changed with Raditude, the band's sixth album, which drops Tuesday. The spirit of collaboration has led to a guest spot from Lil Wayne on the song "Can't Stop Partying," and Cuomo has recently spent time with Adam Lambert and Katy Perry on music. He credits a tiny tour that brought them closer to the fans.

"We did a tiny tour called the Hootenanny Tour," he explained. "We invited fans to show up with instruments, and we had to figure out how to jam with these people we've never met with instruments I had never seen before. It was really challenging and exciting."

So exciting, in fact, that Weezer repeated the feat on Monday's (November 2) episode of "It's On With Alexa Chung," which featured yet another duet between Cuomo and Meester on "I Want You To."