Memorable quotes from Portal depicting the characteristic humor –
Once the tests are complete – and the AI plans to kill you –
(GLaDOS): [near the end of the nineteenth and final test chamber] "Congratulations. The test is now over. All Aperture technologies remain safely operational up to 4000 degrees Kelvin. Rest assured that there is absolutely no chance of a dangerous equipment malfunction prior to your victory candescence. [the moving platform the player is standing on is sinking into a fire pit] Thank you for participating in this Aperture Science computer-aided enrichment activity. Goodbye."
Once you figured your way into the main chamber of the AI, and attempt to shut it down by destroying parts of it –
(GLaDOS): Have I lied to you? [pause] I mean, in this room? Trust me, leave that thing alone.
Portal 2 –
(GLaDOS): Okay look, we both said a lot of things that you are going to regret. (Combined with the characteristic evil and pseudo-cheerful voice in which it is said, this one is a gem!)
(GLaDOS): This next test involves the Aperture Science Aerial Faith Plate. It was part of an initiative to investigate how well test subjects could solve problems when they were catapulted into space. Results were highly informative: They could not. Good luck!
(Wheatley): Most test subjects do experience some cognitive deterioration after a few months in suspension. Now, you've been under for... quite a bit longer, and it's not completely out of the question that you might have a very minor case of serious brain damage. But don't be alarmed, all right? Although, if you do feel alarm, try to hold onto that feeling, because that is the proper reaction to being told you have brain damage.
(Wheatley): They say the old caretaker of this place went absolutely crazy. Chopped up his entire staff... of robots; all of them robots. They say at night you can still hear the screams... of their replicas; all of them functionally indistinguishable from the originals. No memory of the incident. Nobody knows what they're screaming about. Absolutely terrifying. Though obviously not paranormal in any meaningful way.
(Wheatley): You two are going to love this big surprise. In fact, you might say that you're both going to love it... to death. Love it until it kill- until you're dead. [chuckles] All right? I don't know whether you're picking up on what I'm saying here, but …
(GLaDOS): Yes, thanks. We get it. [Chell and GLaDOS enter a elevator] All right, he's not even trying to be subtle any more. Or maybe he still is, in which case: wow, that's kind of sad.