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?"

Time out for a second. That wasn't supposed to happen. Do you see that thing that fell out of me? What is that? It's not the surprise. I've never seen it before! Never mind, it's a mystery I'll solve later... by myself, because you'll be dead.

Your entire life has been a mathematical error... a mathematical error I'm about to correct!

As part of a required Enrichment Center protocol, the previous statement that we would not monitor the test area was a complete fabrication. We will stop enhancing the truth in three... two... zzzt

Area and state regulations do not allow the Companion Cube to remain here, alone and companionless.