Hello.
I've tried for sometime to tell this incident, but haven't found any good places to write it. I've tried with SCP-like fan groups but neh...
I'll relate it from my point of view and from what I can remember:
It was in 2014, probably around september or even january 2015, I honestly can't remember with this horrible memory of mine: I was playing with HOLDKJEFT and hack33rs (now ex-friends) at http://www.roblox.com/games/68699083/The-Mumie-Doll Some guy came to troll around, HOLDKJEFT gave us admin, giving us weapons and then approached to spawnkill the user who then after some minutes told us that he would bring more people to take us out.
The user left, HOLDKJEFT had to go and then hack33rs went on to leave too but I was still chatting with him through Steam. I stood on the server to the side of the spawn with a sword equipped in case the guy came again and see if he indeed was gonna bring "his crew"; I was in 3rd person with the camera facing the front view of my character and the end of the T shaped hallway structure. Of course it's a horror related showcase place, but I saw the progress of it since the major part of the start and he did not add any type of NPCs or enemies.
After all, the guy didn't came back so I was the only one there just for some minutes (as I explained) until I saw a face peeking out of the right wall's corner of the hallway, or at least that's what it looked like. Two white crooked dots that seemed like eyes, a red dot like a mouth and possibly a 3rd white dot like a nose, but the thing is that it seemed as if it was a player: It peeked out facing the direction of where I stood (the spawn area) and then turned back in to the right like a ROBLOXian minifigure would do if it's controlled.
I couldn't take a picture since It lasted there for a couple of seconds until it turned around; it's body was also like a regular blocky character, fully colored black or deep blue and transparent (maybe like Transparency 0.6 or 0.5) but it was visible because of the dynamic lightning of the hallway's wall.
So I just left the server and told hack33rs what I saw. HOLDKJEFT came back after some time (or next day), they both went back to the playground and I decided to follow them in so I could show them where the face character was and the movement it did.
HOLDKJEFT set the lightning to be brighter and took out the dark fog so we could see better around the map, we were there for sometime but it just wasn't appearing (it might only come out in darker zones). Maybe there was Pixellus too (ex-friend), I can't remember but we also told him about it.
We then decided to call the face figure George.
I'm not the only one who's seen this thing around games, it is not something featured on those games either (as I've also said, not an NPC nor real player that appears on leaderboards), There have been forum topics (All Things ROBLOX, Help (Technical Support) with similar experiences about a shadowy figure on unusal places.
Last time I heard someone bring out a "floating face" was when I was playing this game: http://www.roblox.com/games/182781154/The-Maze-Runner-BETA (take notice that this playground has alot of dark and lonely areas) when a person on the chat said that it saw this on the maze.
Here's a quick picture I made of how George looks:
http://vignette1.wikia.nocookie.net/robloxcreepypasta/images/7/78/George.png/revision/latest?cb=20150804033335