Left 4 Dead 2 Easter Eggs

In The Passing; 2: Underground, there is a building that is about three stories high after you get in the green pool and go through the tube. On the ground floor, there's a room where a bunch of refugees were hiding. There's a pool table in the middle... more

There is a diner on one of the levels with a jukebox in it. You have to click it for awhile changing the songs but when you get to one song, it starts playing the credit song from the game Portal.