Grohl "just happened to be in the neighborhood," Axl Rose told the audience; Foo Fighters are scheduled to perform at the same venue as part of their Concrete and Gold Tour on Wednesday night.
In addition to strumming along with his buddies Slash and Duff McKagan as confetti rained down from the arena's ceiling, Grohl also sang backup on the Appetite for Destruction classic.
Prior to the performance, Rose also called Grohl "a lifesaver," likely a nod to the singer borrowing Grohl's massive Foo Fighters throne – which Grohl needed to continue touring after breaking his leg in an in-concert accident – when Rose broke his own foot just weeks prior to the Not in This Lifetime tour.
"I lent the throne to Axl Rose because he broke his foot awhile back, and I went to the show to see them," Grohl told Rolling Stone in July. "It was the first time I'd been in the audience, watching someone perform in this thing, and I thought, 'That is the most ridiculous fucking idea.'"
Once adversaries in the early Nineties thanks to the beef between Guns N' Roses and Nirvana, Rose and Grohl ended Tuesday's performance with an onstage handshake and a hug before leaving the stage.
Watch below: Red Hot Chili Peppers' Chad Smith, host of PBS' 'Landmarks Live in Concert,' discuss a new episode featuring the Foo Fighters at the Acropolis.