VIDEO : Katy Perry Pranks a Fan With a Lie Detector Test, But the Joke Quickly Turns on Her

Katy Perry planned to have a little bit of fun with a superfan on Wednesday, but it didn't exactly turn out that way. The singer stopped by the U.K.'s Capital FM to chat with host Roman Kemp and surprise one of her biggest fans. Not only with her presence itself, but also with a lie detector test to prove this 22-year-old girl named Danielle was a massive Katy Cat. While the prank was supposed to be on the fan, it quickly turned against Katy when questions about her hair, clothing and music were presented to the fan. The fan admitted to not liking Katy's new hair and some of her outfit choices.