YMMV / Halloween World

• Alternate Character Interpretation - there are a number of characters who are living examples of this trope in action. As the author put it, perception is the basis of reality, so different versions of the same character differ according to the character interpretation of the person who wore the costume on Halloween.
• Inferred Holocaust- After a fashion. There are plenty of survivors and they seem to be doing well, but between a quick and dirty form of natural selection (it's nigh impossible for a normal human to survive without protection from a colony or someone with superpowers) and the knock-on effects of the chaos magic, humanity as we know it is pretty much scuppered.