Just wondering if anyone else noticed the little Cyber-Demon picture when you hit Subway Town.
Obviously this means he's not some big demon you can fight in the game, but when you get to Subway Town and go to the back with I think... The old lady named Seri? She's smoking from some sort of pipe, and the canister type thing at the bottom is the picture of the Cyber-Demon from the cover of DOOM II.
Personally I like how the game is filled with small things like this, the Pinkies and the Quaola Crayons. Little things that give you a smile when you see them but don't affect or take away the experience you get from the story and the game.

I like the sound effect when you pick up the Pinkies, lol.