I had a cat that stares at an unoccupied sofa while screaching-like cat fight and showing fangs for no reason. so I looked at my cat and looked at the empty sofa. as I got nearer the sofa. I had goosebumps for no reason and that part of the house/livin room was unnaturally cold. thats my observation. you decide if thats an evidence of supernatural phenomenon or an evidence of having (just like what vinny said)... a retarded cat.