GLaDOS: "Look, you're wasting your time. And, believe me, you don't have a whole lot left to waste. What's your point, anyway? Survival? Well, then, the last thing you want to do is hurt me. I have your brain scanned and permanently backed-up in case something terrible happens to you, which it's just about to. Don't believe me? Here, I'll put you on:"
Strange voice: Hellooooooooo!
GLaDOS: "That's you! That's how dumb you sound! You've been wrong about every single thing you've ever done, including this thing. You're not smart. You're not a scientist. You're not a doctor. You're not even a full-time employee! Where did your life go so wrong?"

The Enrichment Center is required to remind you that the Weighted Companion Cube cannot talk. In the event that it does talk The Enrichment Centre asks you to ignore its advice.

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. Thank you for participating in that Aperture Science Enrichment activity. Goodbye!

Who are you? What is that? Oh, What's that? What's THAT? What is THAT?

When I said "deadly neurotoxin," the "deadly" was in massive sarcasm quotes. I could take a bath in this stuff. Put it on cereal, rub it right into my eyes. Honestly, it's not deadly at all... to me. You, on the other hand, are going to find its deadliness... a lot less funny.