1. Sleep Paralysis
No, it's not a demon sitting over you, you're INSIDE the dream. Also Crop Circles, there's an explanation there.
2. I know many people are generally freaked out to realize that there is, in fact, a spooky skeleton inside you right now.However, science tells us it should be there.
3. There are a few instances in historical texts of exceptionally bright, "heavenly" lights in the night sky, so bright they're even visible during the day (eg. the star guiding people to Bethlehem on Jesus' birth, though I'm not sure if this particular example can be explained by this).It is likely that these were distant supernovae.
4. Hauntings - cold spots, feelings of dread, hallucinations - are often carbon monoxide poisoning.
5. You know how people that "died" and were brought back and they say they saw heaven? Yeah that's a hallucinogen called DMT and it's responsible for your dreams, it releases in mild doses. But when you die a lot of it goes to your brain to create a very vivid hallucination. The same effect can be achieved by drinking ayahuasca tea.