One day a tortoise will learn how to fly.

If you really want to upset a witch, do her a favor which she has no means of repaying. The unfulfilled obligation will nag at her like a hangnail.

The Assassin moved quietly from roof to roof until he was well away from the excitement around the Watch House. His movements could be called cat-like, except that he did not stop to spray urine up against things.

You can't remember the plot of the Dr Who movie because it didn't have one, just a lot of plot holes strung together. It did have a lot of flashing lights, though.

I once absent-mindedly ordered Three Mile Island dressing in a restaurant and, with great presence of mind, they brought Thousand Island Dressing and a bottle of chili sauce.

The trouble was that he was talking in philosophy but they were listening in gibberish.

There are no inconsistencies in the Discworld books; ocassionally, however, there are alternate pasts.