A joke on Youtube where you type 666 on the end of the URL and refresh that Youtube page 666 times and the background of the page will become scary and a creepy ass video will play. Scary sounds will play in the video and at the end of it a hand will come out and grab you.
Pretty fucking scary when you see the video by nana825763.
Jack: OMG dude I just saw the Username: 666 video! I'm so scared!