The Brain, Mind, and Language site has a page with short descriptions of four different rare neurological syndromes.
People with "Kluver-Bucy Syndrome" try to put anything they can get their hands on into their mouths and will "typically attempt to have sexual intercourse with it."
People with "Capgras' Syndrome" think everyone around them is an impostor. They feel like they are living in a real life version of Invasion of the Body Snatchers.
People with "Cotard's Syndrome" believe they are dead — walking corpses. "The French physician Charles Bonnet described a lady who insisted of dressing in a death shroud and being put in a coffin. She demanded to be buried and when refused, remained in her coffin until she died several weeks later."
People with "Fregoli Syndrome" see everyone around them as the same person. It must be like seeing the Oompa Loompas in Burton's Willy Wonka Charlie and the Chocolate Factory, which were all played by the same actor.
