Katy Perry stunned school leavers in Australia on Friday (13Aug10) when she crashed a student prom in Melbourne.
The I Kissed A Girl hitmaker made an impromptu appearance at the city's Grand Hyatt hotel, where pupils were celebrating their leaving party.
The star asked to speak to the head of the student council, and offered to join in the celebrations.
Student council president Anthony Lay says, ''Someone came over to me and said Katy Perry had heard about our formal, and wanted to come. But she's a celebrity and there were more than 550 students in the room, so another person, a woman, said it would be too dangerous."
But Perry ignored the safety advice and stormed straight to the centre of the dancefloor, grabbed a mic and started singing Beyonce's hit Single Ladies (Put A Ring On It) - before the shocked DJ started spinning her recent hit California Gurls.
In a post on her Twitter.com page, she wrote, "I totes (totally) just crashed a prom!''