Who Is That Masked Stranger Standing Next to Michael Fassbender?

Michael Fassbender can now add “rock star” to his already impressive résumé.

The 37-year-old actor plays a very peculiar musician in the upcoming Frank, a U.K. comedy-drama that’s been garnering strong reviews since its Sundance premiere in January. The film follows a young would-be rocker (Domhnall Gleeson) whose life is turned upside down after he joins a band fronted by an eccentric lead singer (Fassbender, in the title role) who conceals his identity beneath a giant papier-mâché head.

Over the past few days, Fassbender has been taking his act all over New York — performing with his onscreen band on The Colbert Report on Wednesday, and dancing around like a human bobblehead doll at the movie’s premiere party the night before. But who’s that standing next to the actor — and assuming his onscreen Frank identity — at the afterparty? Turns out it’s none other than Fassbender’s ex-girlfriend Zoë Kravitz, with whom he starred in 2011’s X-Men: First Class. (They’re not back together — she was only there to help support the film.)

Joining Fassbender onstage at Tuesday night’s event were his bandmates in Soronprfbs (yes, that’s spelled correctly): Gleeson (who’ll be appearing in Star Wars: Episode VII), Maggie Gyllenhaal (Crazy Heart), Carla Azar (Sucker Punch), and French actor François Civil. The actors actually performed as a band during filming — you can hear their single “I Love You All,” taken from the soundtrack album, on iTunes.

So what did Fassbender think was the hardest part about having to act while wearing a giant head? “What was difficult was singing and speaking, because everything inside this box reverberates,” Fassbender told reporters on Tuesday. “In terms of the acting, it was quite liberating to hide behind a mask. It encourages a certain level of mischief — I wish I could do everything in the head, to be honest.”

Frank opens in selected theaters on August 15.

Photo credit: @zoeisabellakravitz/Instagram, Getty Images, 20th Century Fox