Tulpas

There is an unusual little community on Reddit called /r/Tulpas. It is a community of mostly teenagers and young adults (one must assume, based on writing style and references to school) who are trying to deliberately invent something like imaginary friends. The key point is that such characters take on a life of their own, surprising the "host" and acting more or less independently. Granting that most of what is going on is a combination of people playing pretend and people fooling themselves, it's still a fascinating topic. It brings to mind:

• multiple personality disorder
• hearing voices 
• multimind theory 
• empathy 
• predicting what others will do by simulating how you would behave in their shoes (and the golden rule) 
• Hofstadter's strange loops 
• stories of guardian angels and devils 
• ghosts of loved ones
• the process of writing fictional characters 
• group intelligence 
• the subconscious 
• hypnotism 
• lucid dreaming 
• The Bicameral Mind 
• Inside Out 
• An Incredible Mind 
• Fight Club 
• Calvin and Hobbes