On the TV show this Sunday, I mentioned a short story to a caller just before the closing credits. Because one person has already emailed me to ask where to find this story, I'm linking to it here:
An Epistemological Nightmare by Raymond Smullyan.
The reason I brought up the story at the time was because the caller asked something about (I think) whether you can know something, but not know that you know it. I always found this story kind of funny. I admit that I didn't actually know that the story was online when I recommended it, but I was making a reasonable guess that it would be. I just didn't get the name right.