You never know what you're going to get at a Foo Fighters show these days, and at the band's Sept. 19 stop in Anaheim, fans were treated to a truly unusual spectacle: Yes singer Jon Davison coming up onstage to join them for a cover of the Rush classic "Tom Sawyer."

As drummer Taylor Hawkins informed the crowd in the above fan-shot footage, Davison's presence onstage wasn't as strange as it might seem at first glance. "He's one of my best friends of all time," Hawkins explained. "I mean, I've known him since I was in second grade. He's here tonight, and we'll have him do a song with us."

It was Hawkins who got Davison his gig with Yes by repeatedly telling bassist Chris Squire that he'd be a great fit in the lineup if they ever needed a new singer. After Davison's predecessor Benoit David dropped out, Squire reached out — surprising Davison, who later told the San Diego Union-Tribune, "I wasn't even aware or anything until Taylor called me and said that Chris had asked for my phone number."

Davison indulged in a little reminiscing after greeting the crowd in Anaheim, warning fans that "Taylor and I were the biggest Rush nerds in high school. Mullets and everything." But their shared Rush love wasn't the only reason they decided to tackle "Tom Sawyer" at the gig.

"We tried to learn a Yes song, but we didn't have enough time," Hawkins explains in the clip, just before Grohl interjects the main reason for doing "Tom Sawyer" instead of something from the Yes catalog: "They're too f---ing hard!"

Of course, as Foo fans are aware, "Tom Sawyer" has become something of a set list staple in recent months — they covered it in Rio de Janeiro in January, and invited a fan to perform it with them in August. But if anyone's going to cover Rush in concert, it should be the guys who inducted them into the Rock and Roll Hall of Fame, right?

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