I'm posting it all (including the newly released second half), because everyone reading this thread will probably want to read it. EDIT: Fine. Whatever. Excuse me for trying to make your life a little simpler.
The dark humour's getting
really dark now. Also, frickin' huge Portal 1 spoilers ahead.
http://www.thinkwithportals.com/comic/
So yeah, it's definitely Ratman and he was alive and actively helping Chell during Portal 1 (though he was responsible for her ordeal in the first place). Also, yay at CCube.