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

The pop star 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.

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

Check out the video:

The singer posted a picture of herself sat in the cinema on her Twitter page and wrote:

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

Check out a preview:

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