Among her many threats and quips during the boss fight, GLaDOS has a few interesting lines about what's going on outside.
Are you trying to escape? Things have changed since the last time you left the building. What's going on out there will make you wish you were back in here.
I have an infinite capacity for knowledge, and even I'm not sure what's going on outside.
All I know is I'm the only thing standing between us and them. Well, I was.
These could just be baseless threats, but with Portal and Half-Life being set in the same universe, it's generally believed that GLaDOS is talking about the Combine, an alien race and major antagonist of the Half-Life series that takes over Earth between the events of Half-Life and Half-Life 2.
Guide listing help
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "What's Going On Outside?" in Portal. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.
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