Let's make it clear: Having a mental disorder is no fun. Even if some of them kind of sound like fun.
For instance, there is a whole list of mental disorders that basically turn your life into a live action Hollywood movie.
7Capgras Delusion - Your Friends are Body Snatchers
There's no one you can trust. Everywhere you look, faces that look familiar stare back with alien emptiness. In the movie Invasion of the Body Snatchers, humans are replaced with identical alien pod people, making it impossible to trust anyone, stoking paranoia and giving Donald Sutherland an excuse to sport an exquisite sex offender mustache.
If you have the unwavering belief a loved one has been replaced with an impostor (and you don't have the pimp mustache) you're probably dealing with Capgras Delusion. Besides being the name of band you were in while at community college, Capgras Delusion is brought on by that Molotov cocktail of brain disorders: schizophrenia.
The alleged impostor can sometimes be perceived as a threat or simply as a docile stranger who just happens to look exactly like your spouse and inexplicably wants to live their life. While most Capgras patients decide to live with the impostor, some rebel against the perceived takeover and try to fight it. They can become so paranoid that they even believe they themselves have been "replaced."
The question is, if you think you've been replaced, why were you not replaced with a fitter, more well hung version of yourself? We mean, as long there is a pretend "you" running around, that pretend "you" might as well get pretend laid more often.
6Syndrome of Subjective Doubles - Bring in the Clones
Do you remember the Arnold Schwarzenegger remake of The Parent Trap called The Sixth Day? Where Arnold played a pair of twins that were the result of a guy being cloned against his will?
That scenario has also been the basis of more than one Star Trek episode, only there the clones tend to wind up with opposite personalities of the original, even to the point of assuming outright Evil Twin qualities. It's a classic mindfuck plot, since the one asshole in the universe none of us want to contend with is ourselves.
For delusional victims of the syndrome of subjective doubles, that recycled old sci-fi plot becomes a stark and iron clad belief. Some people suffer it as another symptom of the above-mentioned Capgras delusion.
Sufferers of SSD maintain that they have a twin who looks exactly like them but has a completely different personality, presumably brandishing an evil twin goatee. Sometimes patients even allege there are multiple clones running around, or that their own personality has been copied and pasted into some stranger.
God forbid these people ever actually run into somebody who looks like them, or that they should come across that new Facebook app that has you upload your photo and then tracks down all the other people in the world who look just like you. We'll all have SSD before long.