Showbiz
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The 'California Gurls' singer, who made friends with TV presenter Rose during her last visit to Australia, turned up at the Grand Hyatt hotel at 11pm and surprised students from Melbourne High School by singing along to one of her own songs.
According to the Herald Sun, the teenagers started to scream when they saw Perry with the microphone on the dancefloor.
Perry and Rose both posed with the students for lots of pictures before leaving together. Perry later wrote on her Twitter page: "I totes just crashed a prom!!"
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