Using “old hag” in the “Search” engine yeilds 47 results. There seems to be an “old hag” hype going on. 
“Old Hag Syndrom” - original topic from 2003
“I think my quest for lucidity is over”
“I think I had the old hag as a child”
I once read SP being defined as:
I recently mentioned in this thread:
“OBE re-entry by tricking the mind”
about how “the presence” or “old hag” may be yourself. The senses are distorted and you may be actually afraid of your own physical body, and confusing it as someone else.
This never seems to happen to me. I wouldn’t fear it, and it can actually be used towards your advantage for a great lucid experience if you can overcome the fear.