Aesthetic attraction to these marshmallow ponies is not unnatural. Let me explain to you why, very briefly. A hormonally and psychologically normal human male begins to produce large amounts of testosterone, GnRH, and other sexual hormones around the age of 12-14. We all know this, right? Good.
Now, as to why ponies may seem attractive to certain males that have undergone puberty. Excluding abnormal factors such as fetishims and zoophilia, there is a number of reasons.
* The human has been found to be attracted to members of the opposite sex with symmetrical, average, normal attributes. Known by some anthropologists as Koinophilia, this factor causes attraction by attributes such as a lack of facial abnormalities, blemishes (including moles, acne, scars), fashion items considered "unfit" or unusual for a certain culture (abnormally colored hair, piercings, etc.) Ponies fit a form of Koiniphilic attraction in the sense that their faces are very symmetrical. The enlarged eyes make it even easier to notice the symmetry of their faces. The snout shape can also subconsciously show symmetry. The monocolor skin tone of ponies also subconsciously give the perception of a lack of integumentary blemishes, and gives the message of smooth, clear skin, even if it may be abnormally colored.
* Most males are attracted to longer hair in females. Pony hair (manes) is very elaborate, to the point where achieving some of the hairstyles ponies such as Rarity and Fluttershy in humans is physically implausible. The perception of thicker, healthier, longer hair in ponies can cause attraction in males.
* Neoteny. Neoteny is a fancy term for what many call "cuteness". And i don't mean "that's a cute puppy" type of cute, but the "that's a cute girl" type of cute. Neoteny simply is the characteristic of retaining youthful, infantile attributes after achieving a state of sexual fertility in females. Large eyes (and Irises) , small nose, small body, thinner lips, and large facial expressiveness. In this sense, ponies overachieve. All such characteristics are present in them. I can guarantee every straight, healthy male who has watched this show has seen a pony do a certain facial expression they deem "cute" on time or another.
All these attractions are natural in human males as they give the message of healthfulness and fertility in a potential female partner. This type of neotonic animation is not only seen with ponies, but many other kids shows, and ESPECIALLY in japanese animation. Anime and manga has a saturation of neotonic, Koinophilic characters; a trend usually referred to as "Moe" by anime fans and "otaku". Any of you guys ever wondered why you were so attracted to sailor moon back in the day? that's why.
Now please understand that all aesthetic classification of sexual attractiveness is only in theory and statistic. many people have personal preferences, and cultural as well, to what beauty is. But this might answer why subconsciously some people may find ponies to be sexually/aesthetically attractive.
