New York -Katy Perry reportedly caused mayhem at an unsuspecting five-year-old’s birthday bash as part of her latest music video.

As part of her music video for track Birthday, the 29-year-old singer dressed up as a clown and acted as a mayhem-causing entertainer. The gag included taking a swing at a piñata but hitting a man instead and staging a fake car accident by running out into the road.

While the whole prank was in jest, TMZ claims Katy actually ambushed a real five-year-old’s birthday bash and that most of the guests had no idea what was happening. The website posted a clip from the scene today, shot at Knollwood Country Club outside Los Angeles. In the video a woman storms away from the party in anger, while a small child can be heard saying: ‘Mommy, I wanna leave.’

Katy gave a small preview of the music promo during a recent appearance on Jimmy Kimmel, but it cut out before the supposedly upset reactions. She joked that her undercover prank was top secret and that ‘nobody knows’ about it. ‘I was sick of making gorgeous music videos where I am like’ she quipped. Host Jimmy shot back: ‘People are sick of that; they’re really tired of looking at you.

During her stint on the show the star acknowledged her breakup from John Mayer for the first time. The pair had been in an on/off relationship since 2012 but in February it was reported they had split again. While speaking to a ‘super fan’ on the show, Katy pulled a mock crying face as she exclaimed: ‘At least you have a boyfriend!’ Katy Perry has transformed from young pop star to a wrinkled old lady for her latest music video.

The singer is unrecognisable, with lines, sagging skin and white hair as she plays a boozy retired Vegas dancer named Goldie in a clip from the video for Birthday. ‘Have you ever heard that song The Lady Is A Tramp? That might be about me,’ Katy says in character as Goldie, who is clutching a glass of wine.

The short teaser clip also shows the star dressed up as a princess, an animal trainer and a male Jewish MC.

Katy, 29, also dons a clown outfit, complete with a curly green wig. Speaking in a New York drawl, the clown says: ‘’I saw this thing on Craigslist to be a clown, make a few bucks at the weekend, I’m not a birthday party entertainer, I’m just trying to get some cash on the side- don’t start drinking kids.’ The characters are supposed to be the world’s worst birthday party entertainers.

The singer will unveil the full video on April 24. While she’s been busy becoming other people, Katy recently showed she doesn’t know as much about herself as one of her fans does. The Dark Horse singer agreed to a game of trivia about herself against a fan during an appearance on Jimmy Kimmel Live and lost. Katy and superfan Emily were quizzed about the star’s career in the game - titled Who Knows Katy? And the singer wasn’t quick enough at hitting the buzzer to beat her opponent. Emily even answered more quickly than Katy when asked the name of the star’s parents.