But there is another alternative. What if the Chell from Portal 2 comes from a universe where Portal 1 was consistent with Portal 2? Where in Portal 1 the cubes and the cube droppers were different, and the bts scenes were considerably different?
What if we - who play the game and assume control of the protagonists - have taken part in some dimension crossing between games?

at this entire thread, and people who think about shit like this.