Ghost in the London Dungeon is a shock video on YouTube.

Summary

The prank starts with the text:

"The footage you are about to see is absolutely genuine and was captured by CCTV cameras at the London Dungeon. Look very closely and you will spot a mysterious ghostly figure. Scientists have analysed this video and so far have offered no explanation as to what it is."

The image then shows two black-and-white surveillance monitor screens. On the first screen, you see what looks like a cleaner heading out of view with a mop. After about 34 seconds, the screen switches to a dark room, where a man, with long stringy white hair and black teeth, jumps up out of nowhere with a yell of "YEAAAAAH!!!!!!!" After a pause, the man lies down and vanishes. The video ends with the text:

"Did you spot it?"