Near the beginning of the game, right before you find the single-portal gun, you fall down a shaft and into some water. Wheatley asks "Do you see it?" referring to the portal gun. Then he asks "Also, are you alive? That's important. I should've asked that first." (Transcript not exact).
Then he says "I'm going to work on the assumption that you're alive, and wait for you at the end. I'll wait for an hour, and then I'll come looking for your dead body, and if I find it, I'll bury it."
I didn't really have the time, but if you actually stand there for an hour, will he come? I realize this is pushing the bounds of game development, but it is Valve we're talking about here.