Katy Perry surprises London fans at film screening

Katy Perry stunned fans by making a surprise appearance at a sneak preview of her new movie in London on Thursday (07Jun12).

The I Kissed A Girl singer showed up unannounced to introduce Katy Perry: Part Of Me to a theater full of excited youngsters in the British capital.

She told the crowd, "Hey, hello! Is it alright that I'm here? We're going to watch my movie!" before popping on a pair of 3D glasses and taking a seat in the middle of the cinema.

Katy Perry also posed for pictures with fans and handed out popcorn to the audience.

The singer posted a picture of herself sat in the cinema on her Twitter.com page and wrote, "Had tons o' fun in London today at a surprise screening... Wish I could sit w/ (with) all of u (sic) when u see (the film)."

The documentary, which opens in July (12), features concert highlights and behind-the-scenes footage, as well as clips from her personal life and childhood.