I'm a bit late to the party but I've been thinking a lot about these things. [disclaimer!!! Incoherent ramblings]
In the ancient manga Ghost in the Shell you see the main character have the very same weird pose as GLaDOS:
http://youtu.be/OwdlqquJDK4?t=37s
Then watching all these turrets and other weird things in Portal 2, it reminds me of shells, and where are all the alleged dead bodies of all the workers? Perhaps condensed into the "shells".
Specially considering Companions Cubes can talk
http://youtu.be/jWXrAbtaERw?t=11s
Full comic about Ratt (comic that tells the story between Portal 1 and 2) here it's shown that companion cubes can speak and give advice, thus they must have good knowledge about the facility, and how to operate the system, thus they must have been former employees there.
https://www.youtube.com/watch?v=zmfzOvJuVhQ
Chell = See Hell
Edit 2: Portal 1 you had to incinerate the Companion Cube, but it doesn't actually die, it's all an illusion, bit like the famed Millgram Experiment.
http://youtu.be/x7NtsV0EhdU?t=2m4s
http://youtu.be/q5w6ieaTxGA?t=3m56s fratricide achivement