I believe that today is intended to be a humorous look at yourself. Getting to know your inner self but MPD is no laughing matter. It is a very serious disease that takes a trained doctor to get treat.
This disorder was discovered in the late 1880’s, though it probably has been with us forever, by Doctor Jean-Martin Charlot. He originally called it Hysstero-Epilepsy. It is normally brought on by some sexual trauma suffered as a child. The mind develops different personalities to contend with issues the concious cannot.
It normally falls into a second and perhaps a third personality as the concious tries to deal with issues it has suffered, covering it up so someone can appear normal but on the drop of a dime can turn violent or overjoyed. Often the one afflicted does not even know the other personalities exist. Some have even been known to suffer from a hundred personalities.
At times people can think they are one sex and then the other, they may become a pet or a farm animal, or an extremely nice person turns to a murderer. All the while, the actual personality does not know the others have ever come out. It is as though they are sleep walking.
Probably the best known case is from the fictional story of Dr. Jekyll and Mr. Hyde. Though the story is made up, the author must have had some dealing with someone suffering from MPD. It can be a scary decease, both for the victims, and the sufferer. Doctors have found that leaving the other personalities alone and treating the original personality for whatever caused it to adapt is the best treatment. Often when what has caused the disease to infect the mind the other personalities disappear.
How to celebrate – If you know anyone you believe may be suffering from MPD, get them some help! Read Dr. Jekyll and Mr. Hyde. Watch “The Incrediable Hulk”.