Dr. Jekyll and Mr. Hyde
The title characters in Robert Louis Stevenson's thriller Strange Case of Dr Jekyll and Mr Hyde represent an exploration of the concept that good and evil exist within one person, constantly at war. Edward Hyde literally represents the doctor's other self, a psychopath who is unrestrained by the conventions of civilized society, and who shares a body with the doctor. The names "Jekyll and Hyde" have since become synonymous with a split personality or an alter ego that becomes capable of overpowering the original self.
Read more about this topic: Alter Ego