Marvin was humming ironically because he hated humans so much.

'The difficulty with this conversation,' said Arthur after a sort of pondering look had crawled slowly across his face like a mountaineer negotiating a tricky outcrop, 'is that it's very different from most of the ones I've had of late. Which, as I explained, have mostly been with trees.'

In moments of great stress, every life form that exists gives out a tiny subliminal signal.

The film project has been “twenty years of constipation,” and he likens the Hollywood process to “trying to grill a steak by having a succession of people coming into the room and breathing on it.”

I've never understood all this fuss people make about the dawn. I've seen a few and they're never as good as the photographs, which have the additional advantage of being things you can look at when you're in the right frame of mind, which is usually around lunchtime.

If on the other hand he went to pay his respects to The Door and it wasn't there . . . what then? The answer, of course, was very simple. He had a whole board of circuits for dealing with exactly this problem, in fact this was the very heart of his function. He would continue to believe in it whatever the facts turned out to be, what else was the meaning of Belief? The Door would still be there, even if the Door was not.

Arthur Dent: What happens if I press this button? Ford Prefect: I wouldn't- Arthur Dent: Oh. Ford Prefect: What happened? Arthur Dent: A sign lit up, saying 'Please do not press this button again.