With reporting by Matteo Lane

CHICAGO -- One of the singular traits of festivals like Lollapalooza is the array of musical styles brought together in one place, and the motley collection of fans that they attract.

The result is that there are inevitably certain performers that are relatively unknown to select sects of concertgoers. Fortunately for us, that can create the perfect environment for a little trivia.

So that's what we got into at Grant Park on Saturday, shortly before Charli XCX was set to hit the stage. We found some unsuspecting fans and posed the question: Is this a Charli XCX song title or the name of an adult movie?

Hopefully all those fans stuck around to see Charli's set, where she had the crowd going crazy to songs like "Boom Clap."

Not surprisingly, she was left looking like this after the show. "Post Lollapalooza - DEAD," she wrote. Hope you recovered in time for to celebrate her 23rd birthday on Sunday (August 2). HBD, Charli!