(updated 5/25/19)
There’s a great temptation here for me to go crazy. I’ll refrain from that and just list some of his best lines . . .

The Hitchhiker’s Guide to the Galaxy

  • Time is an illusion. Lunchtime doubly so.”
  • This must be Thursday. . . I never could get the hang of Thursdays.”
  • “You’d better be prepared for the jump into hyperspace. It’s unpleasantly like being drunk.”
    “What’s so unpleasant about being drunk?”
    “You ask a glass of water.”
    (I’m not sure why, but this has always made me chuckle, if not actually laugh out loud. It’s just never not funny)
  • He had found a Nutri-Matic machine which had provided him with a plastic cup filled with a liquid that was almost, but not quite, entirely unlike tea.
  • In those days spirits were brave, the stakes were high, men were real men, women were real women and small furry creatures from Alpha Centauri were real small furry creatures from Alpha Centuari. And all dared to brave unknown terrors, to do mighty deeds, to boldly split infinitives that no man had split before . . .
  • “Look,” said Arthur, “would it save you a lot of time if I just gave up and went mad now?”
  • The ships hung in the sky in much the same way that bricks don’t.

The Restaurant at the End of the Universe

  • It is a curious fact, and one to which no one knows quite how much importance to attach, that something like 85 percent of all known worlds in the Galaxy, be they primitive or highly advanced, have invented a drink called jynnan tonnyx, or gee-N-N-T’Nix, or jinond-o-nicks, or any one of a thousand or more variations on the same phonetic theme. The drinks themselves are not the same, and vary between the Sivolvian “chinanto/mnigs” which is ordinary water served at slightly above room temperature, and the Gagrakackan “tzjin-anthony-ks” which kills cows at a hundred paces; and in fact the one common factor between all of them, beyond the fact that the names sound the same, is that they were all invented and named before the worlds concerned made contact with any other worlds.

Life, the Universe, and Everything

  • The Hitchhiker’s Guide to the Galaxy has this to say on the subject of flying.There is an art, it says, or rather, a knack to flying.The knack lies in learning how to throw yourself at the ground and miss.

(It goes on for quite a while after this — and I love every bit of it.)

  • “One of the interesting things about space,” Arthur heard Slartibartfast saying . . . “is how dull it is?””Dull?” . . .”Yes,” said Slartibartfast, “staggeringly dull. Bewilderingly so. You see, there’s so much of it and so little in it.”

So Long, and Thanks for All the Fish

  • Of course, one never has the slightest notion what size or shape different species are going to turn out to be, but if you were to take the findings of the latest Mid-Galactic Census report as any kind of accurate guide to statistical averages you would probably guess that the craft would hold about six people, and you would be right.You’d probably guessed that anyway. The Census report, like most such surveys, had cost an awful lot of money and told nobody anything they didn’t already know — except that every single person in the Galaxy had 2.4 legs and owned a hyena. Since this was clearly not true the whole thing eventually had to be scrapped.
  • Here was something that Ford felt he could speak about with authority.”Life,” he said, “is like a grapefruit.””Er, how so?”

    Well, it’s sort of orangy-yellow and dimpled on the outside, wet and squidgy the middle. It’s got pips inside, too. Oh, and some people have half a one for breakfast.”

    “Is there anyone else out there I can talk to?”

  • Arthur had a swordfish steak and said it made him angry. He grabbed a passing waitress by the arm and berated her.”Why’s this fish so bloody good?” he demanded, angrily.”Please excuse my friend,” said Fenchurch to the startled waitress. “I think he’s having a nice day at last.”

Mostly Harmless

  • A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

Dirk Gently’s Holistic Detective Agency

  • If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family anatidae on our hands.
  • Let’s think the unthinkable, let’s do the undoable. Let us prepare to grapple with the ineffable itself, and see if we may not eff it after all.

(I’ve often been tempted to get a tattoo of this)

The Last Chance to See

  • “So what do we do if we get bitten by something deadly?” I asked.He looked at me as if I were stupid.”You die, of course. That’s what deadly means.”
  • 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.
  • I have the instinctive reaction of a Western man when confronted with sublimely incomprehensible. I grab my camera and start to photograph it.
  • Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.

And a couple of lines I’ve seen in assorted places, articles, books and whatnot

  • I love deadlines. I love the whooshing noise they make as they go by.
  • A learning experience is one of those things that says, “You know that thing you just did? Don’t do that.”
  • The fact is, I don’t know where my ideas come from. Nor does any writer. The only real answer is to drink way too much coffee and buy yourself a desk that doesn’t collapse when you beat your head against it.