The Nightmare Returns

I am the shadow that stalks you in the night, Being sure to give you a great big fright! I am the thing that lives beneath your bed, Giving a rata-tap-tap on your puny little head! I am the glowing sphere flying here and there, So you better make sure you be so very aware! I am the doll sitting at the end of your bed, So you better go to sleep or you will be dead! I am you walking in an ice-cold sweat, Saying "it was just a nightmare, and that I bet!"