Ghost Illusions in Clouds
From Screamer Wiki
A 30-second screamer that pretends to be an optical illusion video which shows a sad face hidden in a picture of clouds. It then shows a still picture of a cloud-filled sky. But at the end of the video, a grayscale and negative image of pops up with the scream from "What's Wrong With This Picture?" extra loud and played four times.
youtube.com/watch?v=P7hUcbkcJAY