In this fascinating TED talk, the late Oliver Sacks describes cases of Charles Bonnet syndrome, in which visually impaired patients experience vivid hallucinations. What's wild about these hallucinations is that they often involve smaller-than-normal people and cartoon characters.

Sample quote:

"We see with the eyes, but we see with the brain as well. And seeing with the brain is often called imagination. And we are familiar with the landscapes of our own imagination, our inscapes. We've lived with them all our lives. But there are also hallucinations as well, and hallucinations are completely different. They don't seem to be of our creation. They don't seem to be under our control. They seem to come from the outside, and to mimic perception."

I also enjoyed: "Kermit the frog means nothing to me!"

Tune in for an engrossing description of patients who are not crazy; they're just seeing things. Enjoy:

For a transcript, check out the TED site.