OK, so I've beaten Portal 1 two times and I just started my third play through, though this one has something unique none of the others had. The radio seems to be stalking me all of a sudden for no reason. In the second pic, it wasn't there, I turned my back to that ledge, started hearing the song, turned around and there it was on the ledge. Take note that the radio appears in spots it shouldn't be, in chambers it shouldn't be.http://prntscr.com/1tlifxhttp://prntscr.com/1tlj3ahttp://prntscr.com/1tlm4hhttp://prntscr.com/1tlnauhttp://prntscr.com/1tlr3xhttp://prntscr.com/1tltqzhttp://prntscr.com/1tly94http://prntscr.com/1tm0p4
in this one you can't really see it very well, but it's at the bottom of that pit you need to jump in to gather enough momentum for those tall platforms.http://prntscr.com/1tm4am
even creepier is when you get back to that test chamber and the radio is gone.http://prntscr.com/1tn0jm
it even follows you outside the test chambershttp://prntscr.com/1tn21y
And I finished the game. It apparently is in the pipe system at the end, though it's different because it sounds jittery (I couldn't take a clear shot of it since it was well hidden).
These still may not be all of the occurrences.
Does anyone know what is happening here? Is it a well-thought easter egg made by VALVe to appear after you've completed the game a random amount of times? I need to know since it's pretty creepy.
Edit: A thing I forgot to mention, is that it also appeared in the "Smooth Sax" chamber after portal-ing the cube from the pit and after putting the two cubes on the buttons to open the door to the room with a glass roof.
Edit 2: It's the same stalker radio whom if you take it through the emancipation grill it sounds like someone is breathing heavily into your ear.