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.

We are pleased that you made it through the final challenge where we pretended we were going to murder you. We are very very happy for your success. We are throwing a party in honor of your tremendous success. Place the device on the ground, then lie on your stomach with your arms at your sides. A party associate will arrive shortly to collect you for your party. Make no further attempt to leave the testing area. Assume the Party Escort Submission Position, or you will miss the party.

While it has been a faithful companion, your Companion Cube cannot accompany you through the rest of the test. If it could talk - and the Enrichment Center takes this opportunity to remind you that it cannot - it would tell you to go on without it, because it would rather die in a fire than become a burden to you.

Well, you found me. Congratulations. Was it worth it? Because despite your violent behavior, the only thing you've managed to break so far... is my heart. Maybe you could settle for that, and we'll just call it a day. I guess we both know that isn't going to happen.

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?"