==Hidden Song on Radio - Exile Vilify==
Go to Chapter 2, Chamber 3. When you enter, go to the door and turn right. There is a Ratman den. Also, make sure you shoot a portal somewhere in the chamber for you to escape later. When you drop into the den, go to the left and there is a corner with a radio. The radio plays "Exile Vilify" by The National. You can take it anywhere in the chamber, but GladOs will destroy it if you go through the Emancipation Grid (awwwww). This track is on the Portal 2 Soundtrack, but many people got confused where it came from.

==Hidden Co Op Bot (SPOILERS)==
At the end of the game you'll see GlaDOS and both co op bots, but if you play the chapter the itch and go to testing chamber 16 he says "I need an exit." So he mashes 2 test chambers together to make one. The thing is one of the must've been a co op testing chamber because if you zoom in to the other chamber really fast when he speaks, you can see the orange bot from co op. Be fast because he will run off. HAPPY HUNTING!

==Borealis Drydock==
At the end of chapter 6 (in the area where you get POTaTOS), go to the bottom floor of the building POTATOS is in. In the back left corner there is a door half hidden behind a book case. Go through the door, continue to the end of the hallway and go through the blown-open door frame to your right. You will be at a dock with several life-savers with the word "borealis" on them, which is a reference to the missing experiment in Half Life 2: Episode 2.

==That Sounds familiar (possible spoiler)==
On Chapter 2, Test Chamber 6, midway through when you need to press a button to get a Weighted Companion Cube, GLaDOS instead throws trash at you first. One of the items she throws at you is a radio. When you pick it up (or at least get near it), you can slightly hear an instrumental version of "Still Alive," the famous song used during the closing credits in Portal 1.