Found on reddit. Reposted with permission. Link to original source.
All right, after watching the latest episode and not having overthought anything in a while, I felt like writing something. So why not write about ponies? Here’s my hypothesis: every pony of the mane cast represents a personality disorder according to the DSM-IV. To be diagnosed with a particular disorder, you have to fulfill at least four and in some cases five criteria that are typical for that disorder. All statements listed with a bullet point are taken directly from the DSM-IV’s definition. So, let’s get diagnosing.
Histrionic Personality Disorder: Pinkie Pie
Ponies suffering from histrionic personality disorder have one and only goal in life: being the center of attention. As the most recent episode has shown, behind everypony’s favorite fun-loving, good-natured, party pony lurks a deeply troubled and disturbed soul that can only be herself when she’s the focus of everybody’s attention.
- is uncomfortable in situations in which he or she is not the center of attention
That’s Pinkie Pie all right. She has a tendency to burst into the scene and disregard anything else that might be going on. In Applebuck Season she took center stage during the award ceremony for Applejack and had to be reminded that she wasn’t, in fact, the reason everyone gathered in the town’s square.
- displays rapidly shifting and shallow expression of emotions
Remember how during the finale of the second episode she burst into tears and IMMEDIATELY went to announcing a party? Remember how she went from being scared to being excited to being indifferent in Bridle Gossip?
- consistently uses physical appearance to draw attention to self
Her costumes, her uncanny ability to appear anywhere at any time, take your pick. This is Pinkie in a nutshell.
- shows self-dramatization, theatricality, and exaggerated expression of emotion
See above; also, everything about her is theatrical. Remember her song that started a war?
- considers relationships to be more intimate than they actually are.
Remember how she “frisked” Hairity during Bridle Gossip? Yeah, she has no sense of “personal space”, which is why’s she always in everybody’s face. Also, she tried to befriend a dragon in Dragonshy by simply being… Pinkie. She believes her personality is enough to warrant trust and intimacy.
- has a style of speech that is excessively impressionistic and lacking in detail
Her silly willy dilly filler words just serve as packaging for her outbursts.
Also, the story of her childhood she told in Cutie Mark Chronicles was, apparently, horse apples. Yet her transformation into her old Pinkamena persona hints at this part being true: she used to be someone else. This could potentially hint at dissociative personality disorder: delusions, false memory, paranoia etc. are all signs of what is colloquially known as a “split personality”. Maybe she constructed her Pinkie identity as a kind of defense mechanism, to distance herself from a truly traumatic event in her childhood and the attention she receives helps her maintain that defense by legitimizing it. So there may still be some truth in that tall tale she related to the CMC.
Her tendency to mess with the fourth wall could also be considered a sign that she’s not who we think she is. Pinkie remains a mystery.
Narcissistic Personality Disorder: Rarity
Named after Narcissus, some dude who pops up in Greek mythology who was so obsessed with himself that he fell in love with his own reflection. This can be considered the more “introvert” version of histrionic personality disorder; narcissists don’t compete for other people’s attention because they know how godlike they are.
- Has a grandiose sense of self-importance
Welp, that’s a freebie.
- Is preoccupied with fantasies of unlimited success, power, brilliance, beauty, or ideal love
This is too easy.
- Believes that he or she is “special” and unique and can only be understood by, or should associate with, other special or high-status people (or institutions)
Rarity does not associate with the riffraff as evidenced by her problems with Applejack’s conduct during Look Before you Sleep and glorifies Equestria’s high society in The Ticket Master.
- Requires excessive admiration
c.f. her Icarus-like story in Sonic Rainboom
- Has a sense of entitlement, i.e., unreasonable expectations of especially favorable treatment or automatic compliance with his or her expectations
The dogs in A Dog and Pony Show even enabled her sense of entitlement by conforming to it.
- Is often envious of others or believes others are envious of him or her
They devoted an entire episode to this.
- Shows arrogant, haughty behaviors or attitudes
I really oughta stop here. Seriously Rarity, go see a shrink.
- Predominant “name dropper” boasting or suggestion association with people or affiliations of importance.
Just because I’m not a big fan of Rarity, this one’s just for fun. Or petty vengeance: Photo Finish? Hoity Toity? Sapphire Shores? You name it, she’s named it. And associated with it.
Not much to say here. Rarity is what the scientific community refers to as “totally fucking nuts”. Of course, her calling being something entirely superficial only makes it worse. I don’t have much hope for this one.
Paranoid Personality Disorder: Rainbow Dash
Pegasus society is, apparently, much more competitive than any other pony society. We get to see how boastful and brash flying ponies are so Dashie took this competitiveness to its logical extreme: everyone’s your enemy. Trust nopony.
- suspects, without sufficient basis, that others are exploiting, harming, or deceiving him or her
- is preoccupied with unjustified doubts about the loyalty or trustworthiness of friends or associates
Those are both pretty similar and both of course apply to Dashie. “Are you a spy?” is probably the most obvious hint; Dashie is quick to doubt the loyalty of others. This may have something to do with her representing loyalty: unless another pony conforms to her idea of loyalty, that pony has to be disloyal.
- is reluctant to confide in others because of unwarranted fear that the information will be used maliciously against him or her
Dashie tends to get uncomfortable when the situation gets emotional. And of course she refused to tell anyone about her being nervous (if not outright scared to death) during Sonic Rainboom. She also denies being scared of dragons after almost having her rump kicked by one. She must maintain her tough pony persona.
- persistently bears grudges, i.e. is unforgiving of insults, injuries, or slights
Applejack beating her almost made her obsess about defeating AJ (to be fair, the obsession was mutual). And she didn’t intend to rest until she’s beaten AJ; losing is an insult to her.
- perceives attacks on his or her character or reputation that are not apparent to others and is quick to react angrily or to counterattack
She’s quick to consider any offhand remark a challenge. Not to mention that she’s quick to become defensive in general but to her credit, this extends to other ponies.
Despite her initial reluctance, she gladly and warmly accepted her friends’ group hug at the end of Cutie Mark Chronicles. So the treatment regimen is quite simple: more group hugs.
Obsessive–Compulsive Personality Disorder: Twilight Sparkle
See how obvious this all is? Twi’s a perfectionist and an organizational genius. A born bureaucrat. Like Hermes Conrad. Sorta. Well, let’s get going:
- is preoccupied with details, rules, lists, order, organization, or schedules to the extent that the major point of the activity is lost
Is there anything Twi hasn’t learned from a book or made a list for? She consulted a book for a sleepover for crying out loud.
- is excessively devoted to work and productivity to the exclusion of leisure activities and friendships
Oh yeah, this is just, you know, the entire point of the show. Anybody know if Lauren Faust happens to have a degree in psychology?
- is reluctant to delegate tasks or to work with others unless they submit to exactly his or her way of doing things
Most obvious in Bridle Gossip when she completely disregards Spike’s suggestion of a “supernatural” remedy.
- shows rigidity and stubbornness
How she dealt with Pinkie Pie’s paranormal (yet somehow very much real) capabilities.
- shows perfectionism that interferes with task completion
Granted, the latter part doesn’t apply as much but… hey, you only need to fulfill 4 criteria to be diagnosed with OCPD according to the DSM-IV and the other traits are utterly obvious. Also, the show is her treatment: she learns lessons, realizes the biases in her thinking/perception and becomes a more relaxed, stable pony.
Schizoid Personality Disorder: Fluttershy
Interestingly, within the context of the show, she DOESN’T exhibit enough symptoms to be diagnosed with avoidant personality disorder, so this’ll have to do.
- neither desires nor enjoys close relationships, including being part of a family
She left Cloudsdale behind, lives in a tree and almost turns to stone when being introduced to Twi. She’s a lone wolf pony.
- almost always chooses solitary activities
As far as I’m aware, animals don’t count. Also, when she was asked why she wanted to attend the Grand Galloping Gala, she didn’t care about the actual event and was more interested in the otherwise inaccessible garden.
- appears indifferent to the praise or criticism of others
She actively loathed praise in Green isn’t your color, due to it putting her in the spotlight. She doesn’t want to be a part of any of it.
- shows emotional coldness, detachment, or flattened affect
I’m so angry I could just scream!
Granted, she’s mostly reserved because she doesn’t want to upset anyone but she may be a little out of touch with her emotions.
- lacks close friends or confidants other than first-degree relatives
Having 5 friends is probably a lot but still. She’s never really seen mingling with anyone else, is still shy and reserved (even among her friends, as seen in Dragonshy) but is certainly getting better.
Fluttershy may be an interesting argument against classifying a “schizoid” personality as a disorder. She’s happy, enjoys what she’s doing and found a way to be solitary and still help her surroundings. There’s a gradual scale between introversion and an actual disorder, she may be one of the borderline cases – or simply an example why disorders shouldn’t always be determined by the majority’s consensus. Anyway, she can be quite open with her friends so unless she self-identifies her personality as a constraining or impairing, I’d say she’s fine.
Uh… I got nothin’: Applejack
Well… Applejack’s fine. She was the first to realize her obsession over the ticket to the Grand Galloping Gala; she keeps everyone grounded and comes closer to the “only sane pony” stereotype than Twi. Sadly, I foresee some problems with her physical health in the future: like Granny Smith, she’ll sooner or later have to get a new hip. All that applebuckin’ must be hell on her body. She is sturdy, no doubt about that but ponies weren’t built for this kind of excessive physical activity. Coupled with the fact that she comes from a cultural background that apparently values hard work as an end in itself (typical of early capitalist, religious society; c.f. Calvinism and Max Weber’s The Protestant Ethic and the Spirit of Capitalism) she’ll most likely work herself to death and consider it a positive, virtuous thing. Her rejection of Manehattan society at an early age could’ve made the antithesis – i.e. farm life – seem like the only possible alternative to pretentiousness and alienation, thus solidifying her belief in the absolving nature of physical labor.
Hanging out with other ponies (especially unicorns) could turn out to be a positive influence. Particularly Twilight could be her “savior” – they’re not too different personality-wise, their relationship is based on a deep mutual trust and respect and maybe by associating with her, AJ can learn a thing or two about the benefits of intellectual pursuits and simply seeing life from a different point of view.
Well, that about wraps it up. In general, I’d suggest some cognitive behavioral therapy, an SSRI for Dashie, maybe lithium for Pinkie and more friendship. Much more friendship.
Posted by The Editor 
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is the total number of completed castles for that path, and 
is the total number of Princesses being in a castle for that path:
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, we can calculate 
, since each possible total path 
results in 1 Princess being in a castle.)
, the correct calculation is:
probability of being taken and the total number of instances of a Princess being in another castle summed over all paths is 
, we can calculate the expected values for the number of times the Princess is in another castle and the number of Princesses being in a castle:
