On their current tour, we find Foo Fighters cutting loose more so than anybody has in a long time: They brought Red Hot Chili Peppers drummer Chad Smith onstage. At a different show, they covered the White Stripes' "Seven Nation Army" with Dave Grohl's doctor on vocals, all while Grohl sat on his opulent throne, still nursing his broken leg. They were at it again last night (Aug. 12) in Edmonton, inviting a fan named Brian on stage to sing Rush's "Tom Sawyer," which he absolutely nailed. Check out some footage below.

Grohl was skeptical, saying as the fan got on stage, "Oh, this is going to be good. You're trying to tell me your big a-- can sing those high notes?" He then asked his name and said, "Don't f--k it up. Welcome to my nightmare."

When it came time for the first chorus and Brian hit the high notes surprisingly well, Grohl was visibly blown away and continued to be with every chorus after. After the song, an overwhelmed Grohl said, "F---ing Brian! Oh my god! Dude, that was f---ing amazing! Let's hear it for Bryan! Thank you, holy s--t. I don't even know... what the f--k? What was that? Dude! Are you a unic? How did you f---ing hit those notes? Jeez, crazy. You must have been neutered."