Raymond Smullyan was a mathematician and stage magician. He wrote a lot of books on logic puzzles. One of his favorites seems to be "knights and knaves", where an island is populated by two kinds of natives, ones who always speak the truth (knights), and ones who always tell lies (knaves), and a non-native traveler has to wrack his brain finding out who is who. Variants on this puzzle have been done to death in popular culture.
- Wikipedia article about Raymond Smullyan