Though what i do believe is aliens. What i mean is, there could be whole lot other civilazations in the universe which we don't know about. If Big Bang really happened and the evolution process took place, we can't be the only life forms in this universe seeing we are barely visible compared to who knows how big this universe is. And there are billions of other stars also known as suns. It could be possible that their is life evolving around those suns just like we are. So aliens are difinetly possibilities.
Other thing i think possible are these creatures we haven't discovered like say werewolf. I don't think a man changing into a werewolf is quite possible but there could be other species of wolves which are man like. Bigfoot another ex for the creatures and such.
Of all that said. There comes a time where i miss being scared S***less of ghost stories and afraid of going to the basement at night and even being afraid of dark.........in my room.