Portal 2 almost saw the light of day as a game about the past of Aperture Science instead of the future.  Chet Faliszek and Jay Pinkerton revealed that Portal 2 almost went an entirely different route than the original, in a prequel style game.  This would have meant that none of the familiar technologies of the original Portal game would have even existed, and ultimately Portal 2 could have been a much different experience than the one we received recently from Valve.
According to our source, Â Pinkerton said that Portal 2 was originally concieved as a game centered around Cave Johnson as a villain and GLaDOS wasn’t to be included. Â But eventually, Faliszek and the development team behind the game felt that people wanted more of the familiar mainstays from the original game. Â Thus, the inclusion of GLaDOS, Chell, and the Companion Cube in Portal 2.
I think most people that have played the game can agree that getting to see multiple perspectives from the Aperture Science Testing Facility was more Portal than we ever thought possible.