As you may have heard, Foo Fighters frontman Dave Grohl fell off a stage in Sweden last month and broke his leg. The band’s had to cancel a few tour dates to allow him to recover, but Grohl didn’t stop for long. In fact, he designed his own Throne of Rock so he could still look badass with his guitar while sitting, and the band played on.

Unfortunately, the band is still on a slightly relaxed tour schedule (as of now, they’re on a break until August 12), but Grohl couldn’t keep playing at all without the help of Lew Schon, the orthopedic surgeon who fixed his leg in the first place. So, at a show in Boston on Sunday, Grohl invited Schon onstage to briefly become the lead singer of the Foo Fighters. Schon chose The White Stripes’ “Seven Nation Army” for his moment in the spotlight, because apparently he couldn’t remember the words to “Everlong.” Whoops.