Do you want to make fun of your friends and laugh with their reaction?
Install Exorcist Teaser on your mobile or your friend's mobile phone, set the timer to activate the teaser at the exact time or in a number of minutes from now and close the application. Exorcist teaser sits in the background, without the knowledge of the user, awaiting for the time to be activated.
Then the photo of the girl who is possessed by a demon at the film "The Exorcist" is shown on the screen, while at the same time the mobile is vibrating and the scary voice of a woman is being heard very loud. Thus it looks as if the mobile phone has been possessed by a demon...while your friend is freaked out and desparetely tries to find out how to shut down the application.
Look for "Exorcist teaser" in Google Play
Android 3.0 and up.