Ghost Illusions in Clouds
The video pretends to show a "mysterious ghost", that can apparently be seen in a picture of the sky, purportedly captured by the uploader "and his friends while at home". The ghost is supposedly a black face in the clouds. It then shows a still picture of a cloud-filled sky. But at the end of the video, a negative image of Regan MacNeil from The Exorcist pops up with the scream from What's Wrong?, extremely loud and repeated four times. After some seconds the text "You just got pranked by a screamer..." is displayed.
NOTE: The following video contains a screamer!