Capgras Syndrome is a bizarre delusional disorder that makes people think their beloved family members and friends have been replaced with identical looking impostors. Well, some mutation of that disorder has a 71-year-old man convinced that his cat has been replaced with an impostor, sent by the FBI to keep an eye on him.
A little background on the patient: He had a history of heavy drinking along with multiple head injuries from playing ice hockey and has also been diagnosed with bipolar disorder. 6 years before the cat delusions he stopped taking his anti-psychotic pills and soon became extremely paranoid. He also believed the house was being monitored and believed that people around him were FBI agents spying on him.