So, Portal 2 is awesome. We all know that.
Did you know about the secret conspiracy theories regarding Chell/GLaDOS/Cave Johnson? And did you know I have something to add to them?
Here is the theory:
Chell is Cave and GLaDOS' daughter. Sort of. See, during the game you encounter Cave and his assistant Caroline in the prerecorded tapes that play as you enter the era puzzle chambers. There's also a picture of the two to find, and some say that the picture contains traces of a third person that have been covered up. (I looked at the enhanced picture and couldn't see it.)
While traversing the science fair area, if you look really closely at the potato growing wildly at the end of the row, you'll notice two things. One is that the potato was treated with 'something from Daddy's work'. The other is that it is proudly signed 'by Chell'. Now, since this science fair took place on Bring your Daughter to Work Day, this means that Chell is someone at the plant's daughter - and who better to snag some awesome chemical than Cave Johnson?
GLaDOS is Caroline - or at least, part of her intelligence is. She was placed in GLaDOS unwillingly, according to some sound files ("No, Mr. Johnson!" that were included with the game.
Ah, but wait!
In the 'Boots' promo, a test subject named Caroline is shown bopping from portal to portal only to go SPLAT on the ground. Could it be that Caroline's pleading resistance had nothing to do with being uploaded into GLaDOS and everything to do with being forced to play cliff-diver in a metal room? It would explain why she is so adamant that the scientists and other Aperture personnel need to be killed. (As to why she enjoys testing so much when it killed her? It's build into her body. Even Wheatley got into it, and he was about as interested in Science as my cats.)
This would also explain why Chell is an orphan. Her parents are both dead - one from doing stupid things with chemicals (Cave) and one from either testing (my 'boots' theory) or unspecified nastiness. It may explain why GLaDOS was so eager to taunt her with being an orphan - being an orphan and being overweight (ha) are the only two things that she knows to pick at, because Chell remained defiantly silent in her test interviews. Why would Caroline pick at Chell like that, if she was her mother? There are two theories - Sometimes Mothers Suck and GLaDOS is GLaDOS. Sometimes Mothers Suck is pretty obvious - there are cases constantly in real life where mothers do horrible things to their kids. As for the second, GLaDOS is not Caroline. GLaDOS is made up of several things, one of which is Caroline, who may be easy to override/ignore.
Of course, this could all be wishful thinking. Chell could be just some random chick, GLaDOS could be picking on her orphan status because it was somehow in her file, and Caroline may not have actually died in the Boots video. That's what I love about Portal - ambiguity. :P