The "Psycho-Kitty Dance" - our 8-yr-old neutered male Maine Coon mix has done this since we adopted him at 9-mos-old: whenever he's on a plush or soft blanket he picks up a corner of the blanket, clenches down on it with teeth, arches his back and starts kneading in rhythm with all 4 paws while going backwards in a misshapen circular pattern with eyes completely glazed over. Nothing gets in his way including the other 2 cats. Eventually, he backs up into an odd sitting position with back legs splayed out under him while front paws continue kneading in rhythm, blanket clenched in teeth, eyes glazed over. This goes on 2-10 mins. Any ideas?