Paraprosdokians are phrases in two parts, the second part being rather unusual to the first. (Whaaaat?) Oh, OK, I'll show you:
1. A clear conscience is a sign of a bad memory.
2. We never really grow up, we just learn how to act in public.
3. Knowledge is knowing a tomato is a fruit. Wisdom is not putting it in a fruit salad.
Winston Churchill often used them:
- If you are in hell, keep going.
- (Clement Atlee) is a modest man who has much to be modest about.
And Groucho Marx:
- I've had a wonderful evening, but this wasn't it.
- The car stopped on a dime, which unfortunately was in a pedestrian's pocket.
- I once shot an elephant in my pajamas. How he got in them, I'll never know.
You're very welcome to add any of your own :-)