Where are we going? Are you coming back? What's that noise? Is that a gun? Do you smell something burning? Ooooohh... what's in heeeere?

This is your fault. I'm going to kill you. And all the cake is gone. You don't even care, do you?

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?"

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.

Momentum, a function of mass and velocity, is conserved between portals. In layman's terms, speedy thing goes in, speedy thing comes out.