[gwern]

          'Look, I can explain,' he said.
          Lord Vetinari lifted an eyebrow with the care of one who, having found

a piece of caterpillar in his salad, raises the rest of the lettuce. 'Pray do,' he said, leaning back. 'We got a bit carried away,' said Moist. 'We were a bit too creative in our thinking. We encouraged mongooses to breed in the posting boxes to keep down the snakes...' Lord Vetinari said nothing. 'Er... which, admittedly, we introduced into the posting boxes to reduce the numbers of toads...' Lord Vetinari repeated himself. 'Er... which, it's true, staff put in the posting boxes to keep down the snails...' Lord Vetinari remained unvocal. 'Er... These, I must in fairness point out, got into the boxes of their own accord, in order to eat the glue on the stamps,' said Moist, aware that he was beginning to burble. 'Well, at least you were saved the trouble of having to introduce them yourselves,' said Lord Vetinari cheerfully. 'As you indicate, this may well have been a case where chilly logic should have been replaced by the common sense of, perhaps, the average chicken. But that is not the reason I asked you to come here today.'

--Terry Pratchett, _Making Money_