Katy Perry is one of the biggest pop stars on the planet right now. And the annual Rock In Rio festival has a reputation for pulling the biggest crowds for any fest, anywhere. What could go wrong? Well, anything, as it turns out.

Perry’s Prismatic World Tour is currently working its way through South America, and the traveling spectacle filled up the stage on the weekend for Rio de Janeiro’s massive annual outdoor event.

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As she’s been doing on the road for more than a year, the singer introduced a fan to the stage to share time in the spotlight. On this occasion, Perry's selection was a young fan who appeared to have been living out the events described in "Last Friday Night." What followed was a long three-and-a-half minutes of touchy-feely, awe-struck messiness. "I think she's rolling," muses Katy, who played host to perfection. Watch the clip below.