Username: 666

Username 666 is a very oldest mystery on YouTube when the person went to the channel and refreshing several times. Before it was terminated. The channel uploading gore or fetish videos.

Username 666 video eventually blew up towards international audiences on YouTube

TheTekkitRealm shows the archive of a 4chan post, 3 of the video names can be seen on inspect element or html (view source) 666, Omega Annult Lustful and 私の人形は私の友達で (Watashi no ningyō wa watashinotomodachi de, My doll is my friend)

Origin
In October 7 2007 - A user on 4chan posted about username 666 saying "Has anyone else seen this youtube channel? I stumbled across it cuz I was looking for essay resources. S**'s crazy man, lol i think one of the videos was featured on reddit." with an image