Freakin' Scary Pop Up!

Freakin' Scary Pop Up! is a screamer video might be considered an optical illusion uploaded by YouTube user RandomAnimeChannel in April 2, 2009

Scary Pop Up Video
The video is seen as an moving illusion, you must only prepare to be watched and stare at this illusion, once it reaches at the 30 second mark is suddenly followed by a picture of Regan MacNeil from The Exorcist appears along with the explosion scream.

Link
NOTE : The following video contains a screamer!
 * youtube.com/watch?v=vUwDJePlrfw