BY THE WAY NSFW...
Grohl said, "What's your name? Aw, bleep it, you're gonna be called KISS guy."
Grohl later asked, "Have you ever done this before" and KISS guy nodded. Grohl then put his guitar around the guy's neck. Grohl was impressed that he even brought his own guitar pick.
Then, they launched into the Foos track, "Monkey Wrench." The dude didn't sing but he can play. So, well on the solo that it threw Grohl off, and he couldn't remember the words.