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, 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. But eventually, Faliszek and the development team behind the game felt that people wanted more of the familiar mainstays from the original game. 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.