When my sister and I were younger we used to sleep in the same bedroom on the second story of our house. The bedroom had two beds built into alcoves on opposite walls. My sister has the habit of "rocking" herself to sleep and sometimes during the night if she wakes up. One night I woke-up and couldn't go back to sleep. I tossed and turned for quite a while till I saw what I took as my sister sitting up in the bed. It was dark and I couldn't make out the features too well. I thought that she had woken me up with the squeaking her bed makes when she is "rocking." I promptly told her to go back to sleep. When she wouldn't lie back down I asked her if anything was wrong. Then I noticed her head moving from side to side, like it was looking around. This confused me, and I got up to go see if anything was wrong. I made my way to her side of the room and noticed that she looked pale. She just continued to ignore me and look around. When I reached her bed I noticed that my sister was actually lying flat in her bed, with a pale girl sitting out of her midsection. I lost my breath with the shock and ran to my parent's room across the hall. I was so scared that for a few moments I couldn't even talk. finally I found my voice and woke my mom up. I babbled in fear till my mom took it that I had a bad dream, and sent me back to bed. I edged my way into the room till I was close enough to pull the light cord and turn on the light. I carefully avoided looking at the bed, for fear of what I would see. I didn't sleep for the rest of the night.
To this day my mom thinks that I just had a scary dream, but I was awake too long for it to be a dream, or to even be half awake, and think I saw something. I don't know who or what it was that I saw but this is the most accurate description I can give.