This screamer video was uploaded back in 2006 by the user VenerableDread, the same uploader of the Saddam Hussein Execution prank. It plays an extract from Spears' song "Baby One More Time", then plays it in reverse to great effect (the backwards gibberish sounds a lot like a sex song), and the video proceeds to play it slower, and even slower, and after even slower happens, a photo negative image of a skull appears with a rather funny feminine scream. The ending text is very similar to Jingle Bells Reversed. Many could consider the video a rip-off of it.
NOTE: The following video contains a screamer.