My Little Pony: Friendship Is Magic/WMG/Setting/Ponies

Ponies. How do they work? If you have guesses on other things then:

"Shared Universe guesses go here

Guesses about Equestria itself go here

Guesses on Equestrian Culture go here

Science and Magic guesses go here

Dragon guesses go here

Guesses on other species go here"

"Go back to the Main Setting Guesses page here"

"and you can still go back to the Main WMG Page, here"

Equestrian ponies' hooves are different in form from real life hooves.
Why ponies seems to grab a lot of things with hooves? You may have noticed that their hooves seems to have a lot more possibilities of motion than horses' in real life. This can be explained if we imagine the cornified structure of an equestrian hoof to be a lot smaller than real life ones; thanks to this, there's a lot more space for muscles, allowing ponies to move their hooves (at least the fore-ones) in an almost similar way to human hands. it's also worth of consideration that equestrian arms and legs seems to have a lot more of meat and less skinny than real life horses, which may contribute on their variegate motion system.
 * They have little dewclaws in front like a Merychippus, only nailless and webbed to the main body of the foreleg. We don't see those because of the simplistic animation.
 * And that, together with the small cornified structure, explains why they have more motion than a normal horse. As for why bigger ponies (like Big Mac and Shining Armor) seems to have normal size nails, is because.... well, since humans bigger (and more muscular) than normal ones have bigger hands too, same goes for Equestrian ponies. That doesn't mean they have less motion than normals.

Equestrian ponies have no fur: they have colored skin.
In "The Best Night Ever", Applejack said that ponies are always naked (when they not wear dresses, of course). Now as we all know horses and ponies, just like any other animal, have their coats who works like natural clothes for them, so in theory the are never naked. Plus there's also the fact that Equestrian ponies can make "additional fur" (aka beard) to grow up in their face, which doesn't make much sense for animals covered by fur (well, unless for some species like lions or sheeps, but not horse). So the only natural conclusion is: ponies in Equestria have skins of varios colors, not fur, which also explains the need of clothes.
 * Jossed: Snips and Snails had embarassing bald patches of skin showing after they got glued together.
 * Don't know if it counts as canon, but the lyrics of "Equestria Girls" mention "furry coats."
 * In regard to the Jossing above, perhaps ponies have very fine/short hairs similar to that of whales and similar ocean mammals, causing it to blend into itself almost non-noticeably while allowing manes, tails, and facial hair to form as well.

The Ponies of Equestria are omnivorous.
The whole vegetarian thing is a cultural tradition. Evidence for predatory capability is in their physiology. First, position of eyes on the head indicate excellent binocular vision. Depth perception is of much more limited use to a herbivore, especially one more adapted to plains. Second, highly developed jaws. The ponies have demonstrated extreme mandibular strength by dragging ropes and other heavy objects with their teeth. Applejack and Rainbow Dash have both demonstrated sufficient jaw strength to support their entire body weight. This might indicate that the ponies have enough strength to bring down large prey, on the other hand this would be of little to no use for a herbivorus life style. Third, the ponies have demonstrated the ability to digest more protein than a normal horse. Pinky Pie has on hand an egg quiche, and presumably uses eggs in cooking. This indicates a high tolerance, perhaps even a requirement for protein.
 * Well, the jaw thing can be argued that they needed to develop that way because they use their mouths in place of hands.
 * Have you seen a horse's mouth? They can still deliver a nasty bite. Their teeth are not designed for slicing prey, but grinding down tough plant material.
 * Possible reason is that the ponies in Equestria ARE omnivorous, it's that if they ate meat. They'll go under a bloodthirsty rage. disturbing picture dead ahead...
 * what looks like a ham or bologna sandwich on the left, next to the cake
 * It's probably beetroots (there are pink ones). Or rose petals. After all, we know they like to eat roots and flowers.
 * That said, there have been accounts of real, live horses showing indications towards omnivory. Who's to say this wasn't all the more true at some point in the history of sapient, civilized mini-horses, especially considering that predator eye placement of theirs?
 * The Apple family raises pigs, and pigs within Equestria are demonstrated to be no-more intelligent than their real-life counterpart. Pigs are raised IRL for their meat and leather, and they serve no other purpose from an agricultural standpoint. Faust was a bit evasive about the question, implying that the Apples let the pigs live on their farm because the pigs needed somewhere to stay, however the pragmatist would point out that the presence of pigs is the most likely explanation for where Applejack's leather hat came from.
 * There is another (still disgusting) explination. The pigs are farm tools. Pigs will eat almost anything, shit very soil enriching manure and have feet that trample the shit/soil just the right way for crop cultivation. Something the Ancient Egyptians supposedly used them for.

The ponies' hooves are magnetic.
This is why they can sometimes pick up things with their hooves, and it it also explains how Applejack was able to grab onto Twilight's hooves when she was hanging off the side of a cliff in the second episode.
 * To paraphrase Mystery Science Theater 3000, "And if their hooves were metal, that would mean something."
 * And their hooves are made of metal.
 * As long as two things are magnetic they can attract eachother, regardless of if they are metal or not.
 * Earlier versions of MLP toys had a magnet in one of the front hooves on each pony to enable them to interact with accessories
 * Maybe they're not naturally magnetic, but they wear magnetized horseshoes? We can't see them in the show for the same reason we can't see their unmentionables.

Ponies are elemental creatures, and we've only seen three so far.
Earth ponies are... just that. Pegasus ponies are air elemental. Unicorn ponies embody either Fire (the fire of intellect, the "electric" nature of magic, Twilight igniting when sufficiently frustrated...) or Aether/Void/Mana. This either leaves one gap (Water) or two (Fire and Water), depending on how catch-'em-all-y the show wants to get. Celestia and Luna don't manifest sea pony traits because they've only been seen above water, and their hind legs would become a tail and fins under. Either tallness is the "hat" for fire ponies, or like earth ponies they're not visibly magical.
 * Water elemental would be those mermaid ones that the fandom seems to hate so much.
 * Try the Power Trio of body (earth), mind (unicorn), and spirit (pegasus).
 * Ponies are based on the five platonic elements: Unicorns are aether, pegasi are air, sea ponies are water, earth ponies are earth (duh), and fire is represented by Zebras.
 * The three races of pony are all made up of a mix two elements in varying proportions. Pegasus ponies are wind (Dash) and water (Fluttershy), earth ponies are Fire (Pinkie) and earth (AJ, or especially Big Mac), and unicorn ponies are made of sunlight (Rarity) and moonlight (Trixie).
 * Another alternative: Alicorns embody Aether, as it's a fifth element that combines the four.
 * ANOTHER Another alternative: there's a popular theory that Nightmare Moon created a breed of ponies that lives on the moon. these embody Aether

Ponies lay and come from eggs.
While Lauren Faust said that Ponies are born via mammalian means, the platypus is a mammal as well and it lays eggs, so it's possible that My Little Ponies lay eggs. This video also proves it.
 * She said they reproduce by typical mammalian means. Egg laying isn't typical for mammals. Also, Lyra Heartstrings was merely trapped in that egg. She didn't originate from it.
 * Pinkie laid one (although it was obviously a gag.)
 * And quite possibly simply a candy egg, considering the occasion.

The secret to pony magic is that keratin, the material hair and horns are made of is an excellent conductor of it.
What are feathers made of? Mostly keratin. What are manes and tails made of? Keratin. What are horns made of? Keratin with a bone core. Now, bone is also a good conductor of magic, which strengthens a pony's skeleton (which explains how a pony like Applejack was able to fall 40 feet several times, landing on her head or rump without breaking her neck or spine). This also allows ponies to use Prehensile Hair to some effect. This also allows pegasi to wield some form of magic in their wings and coats, and also explains why ponies can use things that seem to require hands with their hooves.

All types of ponies have potential to use some types of magic.
But only unicorns are capable of conciously controlling it with such precision. This theory explains Pinkie Pie's "Pinkie Sense", as well as Rainbow Dash's Sonic Rainboom, the fact some of the other Wonderbolts have been seen trailing smoke or lightning when they fly, and how pegasus ponies can walk on and move clouds as if they were solid objects. (hey, if it requires a spell for non-pegasus ponies to walk on clouds, surely there's some magic involved).
 * Confirmed. Pegasus ponies' weather manipulation (and probably their flight) is magic-based, and earth ponies influence plants and animals.
 * The Pinkie Sense is still unexplained though.
 * Pinkie Sense is probably part of Pinkie's Toon Physics, her ability to do whatever she wants (even to the point of violating normal laws of reality) provided it's funny, makes for a good gag, or is in someway humorous to the ponies and/or the audience. Though she can't control her Pinkie Sense and it seems to come and go as it chooses (probably related to when it would be humorous for her to have said ability). As for how Pinkie Pie has Toon Physics when none of the other ponies do is a different question. One we will probably never know the answer for.
 * Her special talent is making people smile (usually via parties), right? AND her Element of Harmony is Laughter, even. I think we can say that her Toon Physics come from one of the two, presumably the former since she apparently exhibited Pinkie Sense before getting her Element.

Ponies in the MLP universe live longer than Real Life ponies.
Many discussions about the show and the setting that bring up the lifespan act as if the ponies in the show live only as long as real life ponies. My theory is that they live LONGER. Think about it: average human lifespan is much longer than it used to be because we've spent hundreds of years creating treatments and cures for HUMAN ailments. But in a world with a population of sentient ponies with many human-like behaviors and customs, it's likely that they've been spending years coming up with treatments for PONY ailments, allowing them to live longer than ponies in real life.
 * In addition, they've got MAGIC. They can probably cure anything but "some of the more advanced forms of death", like being devoured and digested by a dragon. That's how Twilight survived having an anvil and a piano dropped on top of her--just about every bone in her body was broken and internal organs squished into paste, but unicorn doctors were able to mend her anyway. Bandages and wheelchairs... I got nothin'.
 * This would also explain why dragons, capable of eating ponies, are considered so terrifying: being fully digested is not something unicorn magic can cure.
 * All but confirmed in "Family Appreciation Day," given some information revealed in "Winter Wrap Up." It's stated that the tradition has been in place for "hundreds of years," and this is presumably after Ponyville was founded. Seeing as Granny Smith was there for the founding of Ponyville, it means that she's several hundred years old. It makes sense, seeing as there are only a handful of youngsters - it seems that ponies live ridiculously long lives and don't reproduce frequently, keeping the population more or less constant. It might also explain some of the issues with Vague Age -- ponies that might in fact be decades apart in terms of age would appear more or less similar.
 * It is most likely a continuity flub, however it still makes sense if you see it as a centuries old tradition that was continued by the ponies who founded Ponyville. At any rate, Granny Smith has obviously lived a lot longer than a real-life horse to have witnessed Ponyville go from a single log cabin to a thriving cosmopolitan town.
 * In season 2 finale, Fake Cadence compares Pinkie Pie's wedding reception plan to six-year-old's birthday party, which seems to confirm this - if they had a regular horses' lifespans, six years of age would be a perfect time to get married.

There are no "Baby" ponies.
Like the horses we have here, Ponies are born relatively fully-formed. They start walking and talking soon after birth (Albeit mispronouncing things and stumbling some of the time) and when a pony is weened off it's mother's milk, it's enrolled in school. Here, more complex things like math and reading are taught and there are only three "Grades" Kindergarden, 1st grade and 2nd grade. Around second grade Ponies develop their cutie marks and begin the awkward growth spurts to turn them into adults. About a year after finishing puberty, the pony is ready to mate.
 * Once a pony has his/her cutie mark, they can go into an apprenticeship in the field that their cutie mark has selected them for. It acts as a biological indicator of the pony's ideal career, or at least a general field, so schools only provide a general educational background useful to anypony. If this is the case, the other theories of Twilight Sparkle being in an advanced program overlap well, as she's continuing an apprenticeship under Princess Celestia when her peers have at least become journeyponies in their respective fields, with the possible exception of Pinkie Pie, who works for the bakery in an undefined capacity. This provides a tidy explanation for why she's at Sugarcube Corner rather than with her family.
 * Pipsqueak the Pirate DOES manage to speak in complete sentences despite admitting to being less than one year old...
 *  UH-OH! 
 * Jossed, we've now seen a foal in "The Mysterious Mare Do Well", and it is cared for the same way as a real world human baby.
 * Confirmed! In "Baby Cakes" Pound and Pumpkin Cake were walking, flying, using magic, and talking, all within a month of being born.
 * That's easy enough to resolve: Clearly, the foal in the pram was less than a month old.

The ponies in Equestria have a high female to male ratio as an evolutionary advantage.
At some point in their evolutionary history, survival became tough and food became scarce. To help the population remain afloat, the ponies evolved in a way that made it so colts born will be more likely female than male. Whenever a population needs to grow, it's generally more beneficial to have more females than males. One male can impregnate many females, but a female can only be pregnant with one males baby at a time. Even in humans, pregnant women with high-calorie diets have a greater chance of having sons while those with low-calorie diets are more likely to have daughters, for similar reasons: if the woman is eating less, the body will be more likely to believe that there is some kind of crisis going on that could hurt the population as a whole. This is the case for ponies, but just more extreme. Regardless of diet, ponies will be more likely to have fillies because of this evolutionary trait. While it isn't necessary at the current state of the pony population, it's an evolutionary remnant that still exists despite not serving much of a purpose.
 * On that note, "stallion-swapping" happens a lot; it's simply not spoken of often. And there's no stigma against single mothers.

Both wings and horns are recessive traits.
This would explain two earth ponies having a unicorn and a pegasus.
 * That's not how recessives work, both parents need to have the allele for offspring to inherit a recessive trait. More likely it's multi-factorial (biologist-speak for "it's complicated").
 * It's also might because all ponies have Earth, Pegasus, and Unicorn ancestors in the past. Applejack and the others didn't know because they never mated before. One of the hidden truths for the ponies to unite during Hearth Warming's Eve was because each tribes was in danger of inbreeding, so all three interbreed over the years as a result. So, it's perfectly normal for a Brown Earth Stallion and a Gray Pegasus Mare to mate, and give birth to a Lavender Unicorn Filly.
 * Time lord genetics might further complicate things, though.
 * It's also possible that the unicorn and pegasus alleles cancel each other out to result in earth-pony status, which would be why alicorns are so rare and special, since the obvious approach of simply combining the chromosomes in the pair would not produce an alicorn. Combined with a third allele that is supposed to code for being an earth pony (i.e. providing the farming and nature-related talents), not only would this explain the Cake Family's twins (by Mr. and Mrs. Cake coincidentally both having pegasus/unicorn combinations and by sheer chance resulting in a pegasus/pegasus and a unicorn/unicorn), but may also explain why they aren't farmers like the Apple family and (supposedly) other typical earth ponies: lacking the genes for magical connection with nature and farming, they were not as adept to growing crops in their family history and therefore opted for a culinary career instead, since they were better at it.

Ponies can reduce the weight of objects they're carrying.
That's why sometimes they are capable of great feats of strength while at other times they don't seem particularly strong.

Ponies with mixed ancestry can sometimes get some magic abilities of a different pony type
Pound Cake's surges of super-strength as well as his ability to lift himself in the air at a rather young age may be a result of him having inherited a bit of strength-enhancing earth pony magic from his parents.

Pound and Pumpkin cakes exceptional abilities are not exceptional at all.
They are simply a surging of the magic all ponies have. Magic is shown to force things (including developmental processes) to happen unnaturally, so once it stabilizes they'll have to learn to fly and to use magic normally. Alternatively, it might be something they really CAN do but forget, like how some very young babies can swim but still have to relearn the process when they're older.
 * Also alternatively, for pegasi anyway, it might be a body mass issue. Pegasus foals can fly easily because they have so much flying magic for so little weight that zero effort is needed, once they get bigger, they need to actually learn.

Night Ponies are a separate, but related, race to normal Ponies.
When Nightmare Moon was banished 1,000 years ago, a contingent of Luna's most loyal guards left Equestria, blaming Celestia of trying to solidify her own power by getting Luna out of the way. As Luna was Princess of the Night, they sought out somewhere where the night did indeed last forever...or at least a significant length of it; the poles. With several months out of the year being blanketed in darkness, the loyalists were free to revere their chosen princess as much as they pleased. Outside of Celestia's sunlight though, they began to change. Over the millennium of self-imposed exile, these ponies underwent a rapid evolution, likely accelerated by whatever corrupted Luna, gaining cloven hooves and vertically slitted pupils in addition to darker colors. The loyalist unicorns found their horns changing with each generation, and the pegasi had their wings shift with the new evolution. Eventually, the loyalists became the Night Ponies. Breaking the species differences down. Earth Night Pony: Cloven hooves, slitted pupils, traits common to all Night Ponies. Unicorn Night Pony "Nighthorns": Males' horns became pairs of heavy, curved bull-like horns, while the females acquired sets of slender oryx-type ones. Pegasus Night Pony "Nightwings": Leathery bat wings. When Luna returned from her exile, she sought out the descendants of her guards, and is now helping them reintegrate with larger Equestrian society. Their loyalty to her, even after a thousand-year absence is still fierce, leading to members of her personal guard being recruited from their ranks, explaining the bat-winged pegasi pulling her chariot in Luna Eclipsed.
 * If Luna had this contingent of loyalists, why would she have felt so neglected and disregarded?
 * Compared to the rest of Equestria, this contingent was very small; likely a squad or two of guards, and maybe their families. The vast majority of ponies still slept at night, and didn't enjoy Luna's work as much as Celestia's. I may be mistaken, but jealousy, as much as resentment, was a part of Luna's transformation/possession as anything. Luna had her guards, but, in her eyes, Celestia had everyone else.

Horse is to Pony as Human is to Elf (or Dwarf)
The ponies are a smaller and more magical version of the mundane creature, with extensive natural magic and connection to nature. They are divided into a nature variant like a wood elf, a more magic focused variant like a high elf, and a variant that flies like some forms of faefolk are known to. The word pony is recycled here to denote a fantasy race of small horses just as dwarf is used to describe both little people in reality and a race of fantasy humanoid in literature and myth.

So, the word equine is used much as a fantasy setting uses "humanoid". Zebras and other equines may practice and use magic, but aren't as inherently connected to it as ponies. They persist in a relatively primitive state technologically since they can't manipulate objects as well as the magical ponies, so ponies also fulfill the dwarf or gnome role of being better at making things (and mining gemstones) than their equine brethren.

As an aside, the series in fact seems to carry some parallels with Elf Quest, and one can't help but wonder. The earth ponies may be like the Wolfriders, with mundane animal blood in their line that connects them to the earth more fully. The unicorns are like the desert elves, much more in line with magic and how their society used to run. The pegasi are a bit like the gliders, in that they are a bit more militant and they (obviously) fly.
 * "ponies = elves" makes sense. they seem to be much more inherently magical then most other species (Especially "mundane" creatures like cows, mules, etc. which could all be human analogues.), they are very strong, and they are connected to nature very directly.

Ponies have Ball-and-socket joints instead of elbows
Think about it; the main joint in the foreleg seems to have the ability to bend any which way. Either it's a free-floating joint held in place only by muscle like the shoulder, or it's a ball-and-socket joint. Having it be a free-floating joint makes no sense for a joint you stand on, leaving the ball-and-socket joint. Their musculature must be really interesting.

Foals' instinctive use of their powers is a result of the Centipedes Dilemma.
Pound and Pumpkin Cake are shown able to use their powers in infancy, whereas Scootaloo and Twilight Sparkle have not learned to fly and needed extensive training respectively. The reason for this is that the infants are able to do so by pure instinct, which is why their powers are described as coming in unpredictable bursts. As they grow older and they develop mentally, they lose that instinctive edge and/or end up trying to make their powers happen. They can no longer use their powers because they don't know how to do so consciously yet. So they have to re-learn.

Nearly ALL of the ponies, even the likes of Celestia, are complete idiots.
Shown multiple times, but very well demonstrated in A Canterlot Wedding. Chrysalis herself, for all her attempts at being a Manipulative Bastard, is not the sharpest tool in the shed - sending Twilight to the caves for her to conveniently discover the real Cadence, leaving the exit guarded only by three completely unarmed pony girls, not even trying to get in character whatsoever... Yet she manages to fool absolutely everybody in Canterlot, including Princess Celestia, of whom she is the niece! You'd think Celestia would know her own niece well enough to suspect something?

On another note, Canterlot is in danger of being invaded, so why does Luna apparently sleep out of Canterlot? Had she been there, perhaps together with Celestia they could have repelled Chrysalis. Also, since they have the bearers of the Elements at hand, why wouldn't they entrust them with the Elements while they were there? They're fashinable trinkets and had they done this, Chrysalis would have been blasted off far quicker.


 * In Celestia's defense, she probably hadn't been spending much time with Cadence. Normally she's a very busy Alicorn, and around the time of the wedding she was on an even stricter schedule because she was trying to keep watch for danger. Also, it's never implied or indicated that Luna sleeps outside of Canterlot.
 * Actually, it's exactly in "A Canterlot Wedding" where that is implied for the first time -- Luna flies in from outside Shining Armor's force field to relieve Celestia for the night, and she misses out on the entire changeling invasion.

The "Race" gene is on the X Chromosome
Only Mares can be Alicorns, however it is still a rare occurrance because Not All Genes Are Codominant and may require another mutation or specific set of traits to trigger it

There is about a 50/50 split between colts and fillies in Equestria
The reason there seems to be more females than males is pure dumb luck; Ponyville just happens to have a population disparity favoring fillies. If you were to go visit a larger city like Fillydelphia or Manehattan, you'd get a much more accurate cross-section of the Equestrian population as a whole. Most of the straight fillies in Ponyville are either single, or in long-distance relationships.

Most foodstuffs made by ponies are not fit for human consumption.
Since equines have different dietary needs then human beings (not just a near absence of meat products and the presence of certain plants), their cuisine probably developed to be quite different from human ones. For example, there's probably double the amount of salt in the baked goods then what is considered normal for baked goods made for people.
 * Related guess: Pony food normally has enough sugar to give a human diabetes. A human pancrease just isn't built to handle all of Apple Jack's apple themed desserts and Pinkie's Cakes/Candies style baked goods.
 * Also, Pony food has a LOT of fiber. As they casually eat hay and assorted plant stuff that humans wouldn't eat unless desperately starving. And even then, human stomachs won't get much nourishment.

Pony Teeth are Super Tough.
Since they seem able to use bite force to support their weight without trouble, their teeth are probably stronger than human average. Also the sheer amount of damage ponies can endure (crashing, trampling, etc.) without knocking out teeth is impressive. Lastly, for a race that has a lot of apple desserts, candies, cakes and other high sugar foods, they don't seem to have much trouble with cavities.

Breaking a leg for a Pony does not mean its time for a Mercy Kill. They can actually get better from that.
A combination of healing magic, extreme durability that goes to cartoonish range of toughness and being smart enough to have medical care probably allows them to be treated where real life horses would have to be put out of their misery.

When Young, Boy Ponies Will Be Stupid.
Still a new fan but while the girls seem like a gifted bunch, the boys are dumb enough to go bear baiting with themselves as bait. Thankfully the stupid seems to wear off at maturity.

Alicorns are the Progenitor Race of all Ponies
Less of a WMG, and more of a serious theory, This Troper believes Zebras, Donkeys, and other equines in show have the same common ancestor species, similar in a way to the earliest species under the Homo genus for humans, though this is probably obvious. I call this Equus progenitori. b) following this is theory, Equus caballio (Ponies) are a species, unlike Ponies in the real world, which are merely a variety of Equus ferus caballus (Domesticated Horse). Equus alicornus would be the progenitor ancestor race of modern ponies, Celestia and Luna representing some of the only living ones. the varieties are simple genetic markers that all ponies carry, but not it's very rare or impossible for a modern pony to show genetic markers of all three "breeds" although it is technically possible for an Alicorn to be born to any other ponies, if the Genetic markers expressed properly. The following is the taxonomic hierarchy:
 * Genus - Equus
 * Common Ancestor - Equus progenitori sapiens
 * Species Zebra - Equus zebra sapiens
 * Species Donkey - Equus asinus sapiens
 * Species Alicorn - Equus alicornus sapiens
 * Progenitor Subspecies of Modern Ponies - Equus caballio sapiens
 * Earth Ponies - Equus caballio terra (also known as Equus terra)
 * Unicorns - Equus caballio monoceros (also known as Equus monoceros)
 * Pegasi - Equus caballio pegasi (also known as Equus pegasi)

Ponies are Programs.
Equestria's world is a node in a Re Boot/Tron universe inside a computer. That's why ponies have to move the sun and the moon, control the weather and generally micromanage their entire environment. But unlike Reboot or Tron, they don't know it.

The ponies of Equestria are semi-divine servitors created to uphold the natural laws.
All the ponies have some manner of innate talent, whether magical (Fluttershy can control animals, Pegasi control the weather) or mundane like Apple Jack's skill at herding animals. We're told that the world outside of Equestria does not require the maintenance Equestria does; animals take care of themselves, as does the weather. But this is not a sure thing. In case of a breakdown of the natural laws, Celestia created servants that might keep things running smoothly so she herself could focus on fixing the underlying problem. She made Equestria exempt from some of these laws so that the ponies would not forget the skills required. The ponies with mundane skills are to collect the practical knowledge of civilization so that even if all life outside of Equestria is destroyed through some cosmic SNAFU, rebuilding will be possible. They were given free will because Celestia and Luna needed the company.
 * Ah, but is the Everfree Forest the norm (suggesting all lands beyond Equestria work that way) or an aberration (suggesting you could circumnavigate the Forest while remaining in Equestria)?

The ponies of Equestria are evolved from System Shock 2's Annelids.
Exaltation of harmony and fear of discord? Check. Advanced psionic abilities? Check. No advanced technology like computers? Check. Now all that's needed is a Creation Myth where a Machine Mother gives life to the first ponies, tries to destroy them, and is killed by her own pawn.

The ponies of Equestria are Sufficiently Advanced Aliens.
Look at the evidence. They control the weather and the landscape. They've domesticated animals to the point where said animals have forgotten how to take care of themselves. (Sound familiar?) Their society is ludicrously advanced compared to humans. They even have Functional Magic for Celestia's sake! The ponies never seem to question any of this, and are horrified at the thought of nature taking care of itself. Obviously, their technology has advanced to a level in which the ponies themselves don't fully understand how it works, it "just is". (Kinda like the attitude many humans in developed countries have towards advancements such as computers, medicine, and and democracy.) This perfectly explains all the Schizo Tech. It's SCIENCE, people!
 * Which probably means that they are all just one disease away from a global plague.
 * And they know it: they are deathly afraid of Cutie Pox when Applebloom gets it.

"Pegacorns" were the Sufficiently Advanced Alien Precursors; the rest are their descendants.
The singular nature of Princess Celestia and her sister raises a few important questions. They would appear to be an ancient breed of pony that has evolved into the smaller, shorter-lived ponies of today; but if "pegacorns" are so long-lived, why haven't more of the same generation survived into the present day? If they were killed off in a war or something, how did a couple of survivors get to rule over all the other kinds? Most importantly, how could any ponies predate their own solar cycle?

What would make sense is if horses with both horns and wings were a highly advanced race of interstellar nomads who made it their mission to use their cosmic powers to terraform planets and seed them with life. During the founding of Equestria, the aliens could have interbred with the most compatible of the native fauna to produce generations of "little ponies" that would inherit diluted forms of their powers, enough to look after the local environment. As part of their tradition, after some time the pegacorns left the planet to seek out a new one, leaving behind only a few of their own as guardians to keep the big things like the orbits and rotations of the planets in balance. This could be because they are very vulnerable to losing their sanity and fracturing their personalities from boredom, such as what happened to Luna.

We know Princess Celestia enjoys a good prank; it's likely to be one of the ways she keeps her sanity in check. But Celestia's Magnificent Bastard side may be part of a serious plan to set up groups of ponies on tests to see if they can harness forgotten technologies like the Elements of Harmony and eventually govern the planet all on their own someday. Additionally, Celestia's extraterrestial nature would explain why she insists on keeping the title "Princess" after so many years as sole ruler: The real King or Queen of her society is still out there, only on some other planet. And her interest in Twilight Sparkle's reports on friendship may be because Celestia is compiling a sort of cultural/anthropological study on what sort of people the pegacorns have produced, and a personal account from one of them is just what's needed to make it really convincing.

The ponies of Equestria evolved from prehistoric horses.
Horses are to Equestrian ponies as neanderthals are to modern-day humans. Thus, the reason we don't see any horses on the show is because they're all extinct.
 * Not an accurate comparison, not all modern humans are descended from neanderthals, and those who are are hybrids. Ponies were bred from horses through inbreeding of a single species.
 * Beat me to this guess

The ponies were once a slave race.
Long ago, the Diamond Dogs ruled over Equestria with an iron paw, using the ponies for manual labor. Earth ponies were used for digging and hauling wagons, unicorns were forced to use their magic powers for gem-finding, and pegasi were used as flying mounts for personal transportation. One day, an alicorn were born- Celestia and Luna's mother- and given to the tyrannical queen of the Diamond Dogs as her personal pets. After many years of seeing her kind enslaved and abused, the alicorn overthrew the queen and revolted along with the rest of the ponies, forcing the Diamond Dogs to live underground in the very mines they once forced ponies to dig in.
 * Except that in "Hearths Warming Eve", it was clear that the ponies (who were in charge of their previous land) migrated to what eventually became Equestria. Given what was said, this was before Discord or the Princesses came into the picture. They really couldn't have done that if they were enslaved; even if they had been, it would have been by the Windigoes, not by the Diamond Dogs.

The ponies are a colony of terraformers.
From the start, Celestia and Luna made sure that the planet spun at the correct speed, and disagreement over it lead to their conflict. It's been several generations for most ponies, who can't recall their origins, but most jobs involve creating an Earth-like environment artificially, up to and including the feeding and wrangling of "wild" animals. Equestria is the area that's reached a desired state, even if it still requires maintenance from the ponies. The Everfree Forest marks the edge of their efforts, as Fluttershy says that the "animals take care of themselves" and thus a self-sufficient ecology can be found. Zebras are an intelligent native species, just different enough from ponies to provoke an Uncanny Valley reaction when they're first introduced to one. Parasprites are another native species which is normally controlled by predators in the wild areas of the planet, but acts like an invasive species when introduced to Equestria (when Celestia was called away to deal with an infestation at the end of the episode, it was because she's old enough to be considered an expert on the native species of the planet). Dragons are an interesting case, as they are a native species that's somewhat socialized, and Spike is an early attempt at domesticating one.
 * The original inhabitants were nonsentient Draconequi that produced a hallucinogenic substance that gave Ponies the ability to navigate interstellar spacecraft. After the planet was colonized by the Empire of Pony, Celestia and Luna became alicorns by consuming gratuitous amounts of it, then "ordered" the local environment in a way that caused the Draconequi -- other than one smart freak -- to go die out, but made it more hospitable to Ponies as part of a prescience-informed millenia-long plan to ensure that Ponykind never goes extinct. Dragons are (so far unsuccessful) attempts to engineer Draconequi that can exist in the ordered environment.
 * And with that I think we've managed to cross over MLP with every major 'verse in literary history.
 * In light of Hearth's Warming Eve, this can be amended thusly: The first colonists seeded were the three core tribes of ponies fighting against the chaos of the world they lived upon. The intelligence that was Discord allowed them around because it was adding one new chaotic element, and they fought among themselves, too. At the end of the play, though, we see an Equestrian flag displaying alicorns. Alicorns were not the root of ponykind. Alicorns were prophesied to emerge, a second phase of the terraforming project that would create a unified administration once the pony population was large enough. Once Luna and Celestia appeared on the scene and gave ponies real direction, Discord took notice, leading to the confrontation that utilized the Elements of Harmony. In the years that followed, Luna was banished, but because Celestia can organize all of Equestria, no more alicorns are needed from the population at this time. Phase three, once the planet is fully managed, will mean contacting the seeding population, whomever those precursors might be, so that they can live with the ponies who manage their paradise planet.

Originally there were only Alicorns, but Discord split them into 3 races to get them to turn on each other.
Obviously his chaotic magi missed at least 2 of them.

All pegasi have a sort of elemental affiliation that gives them a trail at high speed.
For instance, Rainbow Dash has a rainbow, while Soarin' has a thundercloud and Spitfire has a smoke trail. This is why nobody has ever done a Sonic Rainboom before Dash - as Pinkie said, only a "Pegasus pony like Rainbow Dash", that is,a rainbow pegasus could cause it.

Pegasus ponies don't fly with their wings.
They fly with magic. They can extend their flight magic to things they tow(like chariots, or moving vans), so they fly with them instead of dangling below them. Part of their magic allows pegasus ponies to walk on and manipulate clouds. Their magic, their flight magic at least, comes from their wings, much like the unicorns' magic comes from their horns. That's why Rainbow Dash couldn't fly when Applejack tied up her wings.
 * Word of God confirms that pegasus and earth ponies have magical powers. While she doesn't say that flight is magical it's a safe assumption to make.
 * As an extension to this it is possible that in most cases magic is providing the lift. In those cases the wings are merely acting as stabilizers and forward propulsion. We see evidence of this in Scootaloo, who has yet to master the magic required for lift but is able to use her wings for forward propulsion. Only certain Pegasi can use magic for forward propulsion, the Wonderbolts and Rainbow Dash would be examples. This is visible as the magical trails these Pegasi leave behind.This magic might also explain the Sonic Rainboom. Ponies are not very aerodynamic, so additional magic would be used to improve the aerodynamics of the Pegasus. Additional magical force would be required as forward velocity increases to prevent the Pegasus from being shredded by air resistance. After breaching the sound barrier there is a marked decrease in air resistance, so the magical energy would need to be rapidly dissipated in the form of the rainbow explosion witnessed.

Pegasus magic is not flight, but rather Inertial Dampening.
Pegasi are not what you would call aerodynamic, and routinely pull off maneuvers that would clearly be impossible through physics alone. It's natural to imagine that their flight is boosted by a magical push, but just adding a force vector and calling it "magic" leaves a lot of the questions raised by the feats they demonstrate unanswered. One possibility that goes farther to explain what we see is that instead of adding force, pegasus magic creates a field that reduces or nullifies the mass of the pegasus and any freight that she may be carrying.

Note that cloud-walking and sculpting is not explained by this; even if a pegasus reduced her mass such that the matter of a cloud was a physical obstacle, that wouldn't make her able to pick it up and manipulate it, and at any rate the air itself would be as much of an obstacle. This also implies that the main force that a flying pegasus is struggling against is not gravity but air resistance.

Some evidence:
 * Rainbow Dash's mass is at least on the same order as Applejack's, or she'd have gone flying when she tried to hoof-wrassle.
 * Items hauled by pegasi appear to float, but fall plenty fast when dropped.
 * If the mass does not all return instantaneously, that explains how the frog that Fluttershy dropped, not to mention Twilight Sparkle, survived "Feeling Pinkie Keen".
 * Rainbow Dash, Rarity and three Wonderbolts survived a near-right angle turn at supersonic (and possibly superluminal, given the Discworld magical field theory) speed. If they were close to massless due to Rainbow Dash's magic, the extreme G-forces would not have affected them.
 * Fluttershy seems to have imperfect control over this ability. In episode 2, after a burst of mass compensation when she and Rainbow Dash catch Twilight Sparkle, Fluttershy undercompensates for Twilight's mass, because she's used to carrying smaller mammals. In "The Cutie Mark Chronicles", even though she couldn't gain control of her falling, she was able to reduce her mass enough that a swarm of butterflies was enough to break her fall.
 * When Rainbow Dash is affected by the Poison Joke and her wings are on upside-down, she's still able to move her own weight around. This is particularly visible when she's on the floor and apparently thrust-vectoring downward into it, but it causes her to scoot across the floor as if she weighs nothing.
 * The Elements of Harmony, in their aspect as big stone balls, behave as if they're very heavy when Rainbow Dash and Fluttershy carry them. Are they magic-resistant?

Pegasi don't form families.
It's very strange, but we have extensive knowledge on Applejack and Rarity's families, and we know a bit about Twilight and Pinkie's families, but we know practically nothing about Rainbow Dash or Fluttershy's immediate family, we know even less about Scootaloo's. I don't even recall seeing any Pegasus families. But I hope this is proven wrong at some point...
 * This is because young Pegasi are taken away from their families to work for the princess.
 * Thunderlane and Rumble in "Hurricane Fluttershy" are two pegasus brothers. Still, it may be a strong trend.

Pegasi have toxic feathers.
Considering that a love "poison" was made by stirring different ingredients with a pegasus feather, perhaps it was the feather itself that made it poisonous.

Pegasuses flying is related to the pony's aggression or assertiveness
As we know from the past, the pegasuses were a Proud Warrior Race styled on the Romans. Now a good deal of their culture is based on competition and many of them are jerks. Rainbow Dash is the best flier in Equestria. Fluttershy often seams to forget she even HAS wings. That is unless she is angry, then she stops walking in favor of flying and even was able to go faster that Rainbow Dash. The flight training is designed to get more aggressive ponies because aggressive ones are better with their wings.

Unicorns are naturally predisposed to having mental disorders.
Maybe it's due to utilizing magic through an appendage that's so close to their brain, but it seems like most of the unicorn cast members appear somewhat... neurotic. There are several claims of Twilight having Aspergers, Rarity being Super OCD and even Sweetie Belle being a crayon short of a box. Even minor and background unicorns come off as a little unhinged, Snips and Snails appear slow, Trixie's a little over-dramatic and Lyra's well... Lyra.
 * So, are we going with the "Pinkie pie is secretly a unicorn" one down there too, she's got a serious case of ADHD and maybe a bit of schizophrenia
 * Not necessarily. "All that is gold does not glitter. All that glitters is not gold." Just because Pinkie's nuts doesn't mean she's a unicorn. She's just fourth-wall-cracking-bonkers.
 * As of Season 2 Episode 3, "Lesson Zero", this theory is gaining more credence. Twilight goes absolutely batshit over the course of the episode!
 * And again in "It's About Time".

Unicorn Magic has something to do with Thelema.
Twilight Sparkle, who is explicitly stated to have Magic as her special talent, has a Cutie Mark in the shape of a unicursal hexagram. Although it's also used in some old Hinduist traditions, the unicursal hexagram became popular through Aleister Crowley and Thelema.
 * I though it was the image of the Elements of Harmony
 * Thinking of it, this makes sense. It's a six-pointed star and we have six Elements. However, it's still a star in the shape of an unicursal hexagram.

Unicorns are specifically vulnerable to compulsive disorders.
Twilight is obsessive-compulsive about organisation. Rarity is obsessive-compulsive about cleanliness and neatness. Trixie is narcissistic, compelled to speak about herself in the third person and promote herself at all times. Prince Blueblood has shown signs of orthorexia (compulsively ordered eating). The children aren't doing too badly, although Snips and Snails have an obsessive hero-worship of Trixie going on. Sweetie Belle seems to be the sanest unicorn on the show.

Unicorns have a personal Pocket Dimension where they can store things
It's called magicspace. Unicorns can store any object in this personal magicspace as long as there is space. It can then be brought back out if the unicorn needs it. This is how Twilight was able to "conjure" a door in front of Spike and one of the Flim Flams was able to "conjure" a poster of their business logo out of nowhere. It's also how Twilight was able to eliminate all of Rarity's confetti and her red carpet. She didn't make them disappear, she stored it away in her magicspace until she could find the time to dispose of it.

Earth Ponies are capable of Necromancy and life-stealing.
With enough practice, an earth pony can twist and corrupt her/his special connection to the land and life to perform a sort of magic involving raising the dead, draining life force, inflicting disease, causing drought and grossly altering animal behavior. Understandably, this magic is forbidden and its mere existence denied by the authorities.

Earth Pony magic connects them to the earth, literally.

 * In addition to being able to bless the land and yield food, Earth Ponies can anchor themselves to the ground, providing them with enhanced traction in concert with their natural strength, and not allowing them to be knocked off their feet through brute force. If an Earth Pony specialized in it, they could feasibly walk on inclines, vertical surfaces, or even completely upside down like any other plane, so long as they were still walking on Earth.

Earth Ponies enhance healing abilities.
Not to the extent of an outright Healing Factor, but still enough to be useful. Earth pony abilities include greater strength and stamina, as well as encouraging plant growth, both of which can be linked to speeding up cell growth and repair. Just being near an earth pony would allow a unicorn or pegasus to heal much faster, which is why a lot of nurses are earth ponies, though they still need a unicorn to actually perform a surgery.

All ponies are born as winged unicorns.
There are actually no different types of ponies. Specially selected and indoctrinated midwife ponies secretly remove wings and/or horns from the newborns. This is done to keep the pony-society stratified with the apparently god-like Celestia on top.

The operation also affects the growth and life-span of the ponies in a negative way.
 * Alternatively, all ponies go through winged unicorn phase in utero, but then hormones/magic suppressed the development of wings, horn or both.
 * Cerapters aren't that uncommon. However, it's vanishingly rare for both horn and wings to develop properly if present at birth. (This explains why Cadance doesn't seem any too powerful; she isn't a Physical Goddess, just one of those lucky few.) As an excessively deformed hornbud will never grow into a proper magical focus (making such foals a danger to themselves and others), and stunted wings are no good for flight, these are amputated before anything tragic can happen.
 * Possibly jossed. When the Cakes had their twins in "Baby Cakes", one was a unicorn and one was a pegasus pony. It was explained that one of the parents had a unicorn ancestor and the other parent had a pegasus ancestor. If Celestia wanted to keep the ponies down by taking off wings and horns, why would they get the children of Earth ponies and only remove either the horn or the wings, and not both? That just seems weird.

Alicorns are celestial paragons.
While Celestia and Luna do move the heavenly bodies, they're treated more like special royalty than gods. Not to mention, they're capable of having distant relatives among mortals (e.g. Blueblood, Celestia's great-great-great-great-great-great-etc. nephew via her mother). There may be all manner of alicorns amongst the heavens, but Celestia and Luna are some of the few who chose to live amongst the mortals.

Normal-sized Alicorns like Cadance are the result of a do-not-express gene failing to transmit.
Normally, interracial foals are merely one of the three types.

"Alicorns" and Changeling queens are directly related and possibly even the same thing.
It's just that where Chrysalis raised her own swarm and went on a straightforward love vampire locust rampage, Celestia and Luna long ago decided to adopt ponykind as their "children" and put in the hours to earn the love that sustains and empowers them. Cadence is essentially the same, only younger (possibly too young to even worry about biological offspring yet). That's also why Chrysalis, who otherwise couldn't care less about the lives of mere ponies, didn't kill Cadence outright; enemy or not, she's still "family".

Alicorns get their wings and ethereal god-manes when they hit some magical peak.
It only happens to the ponies in the royal family. They're born as unicorns, and when they hit a magical peak they get wings. When they hit a second magical peak, they get the "god-manes". When Cadence is helping Shining Armor defeat the Changeling Queen with her magic, her mane temporarily becomes ethereal. Shining Armor has yet to hit either peak because he's lazy.
 * But if the peak is relitive to total power potential, it could just mean he and Twilight are just that powerful
 * Considering that Shining Armor can cover an entire city with a selectively permeable force field I'd guess that those "magical peak transformation" rules are only applicable to the royal bloodline. And since Luna still had her wings after being depowered by the Elements and Cadence had wings as a "teenager" I would speculate that it's just the mane.

Alicorns and ageing
Alicorns age differently from other ponies. Like dragons, their physical and mental maturity is more a function of their current mental state than their physical age. We already know that they (or at least Celestia and Luna) are either immortal or very long lived. We see Luna in three different states. In the beginning of the first episode and as Nightmare Moon she is proportioned like Celestia. Immediately after being hit with the Elements of Harmony, she reverts to an almost child like state. Later, having had some time to recover, she is more mature, but not as mature as Celestia.

This has interesting implications for Cadence. in Canterlot Royal Wedding, she appears to be an adult, but she seems much younger in flashbacks. Perhaps Cadence matures in cycles. While Celestia and Luna have avoided taking lovers, love is too important to Cadence for her to spend eternity alone. Therefore, every few decades, when the right colt comes along, she gets married. Of course, any relationship she was in would be a Mayfly December Romance, and her husband would eventually die. Her grief over her partner's death would then de-age her to a child until she was ready for love again.

This would also allow Cadence to be Blueblood's mother, explaining how he fits into this whole mess.

The original Alicorns were forged as living weapons against Discord.
In the beginning, Equestria was ruled equally between the descendents of the Chancellor of Earth Ponies, General of Pegasi, and Queen of Unicorns, until Discord came. In order to fight against his great power, the three leaders had to create something stronger than Ponykind, a living force of Harmony. By fusing aspects of earth ponies, pegasi, and unicorns, they created first Celestia and then Luna, raising them until they were old enough to harness the Elements of Harmony and overthrow Discord. The old leadership yielded power to their creations as they could provide truly unified leadership for pony-dom. Celestia and Luna took mates early on, before anyone figured out that they were also immortal, breeding a "royal family" that existed as a separate entity down through the ages, some of whom were mortal alicorns.

Ponies are actually born with their Cutie marks.
But they fade shortly after birth, in the hour or so they have them, the parents are given a glimpse of their child in their prime, Then, they give their foal a name which corresponds to this vision. Since the name usually goes along with the cutie mark give or take a little (We have yet to meet a big, rude, scary pony named "Cuddles"), it's sort of a hint the parents are giving their child.
 * Seeing as this theory doesn't really apply to characters like Pinkie Pie, Twilight Sparkle, Rarity, and others, This Troper has an alternative theory for the names. at a Ponies Cutecineira, a Pony has the choice to choose a new name for themselves based on their cutie marks and special talent.

Cutie Marks are not genetic.
Less of a guess then an observation, but Cutie Marks don't appear to be genetic in nature so it might not be accurate to assume that somepony is related to somepony else by cutie marks alone.

Cutie Marks are not determined until they appear.
That is to say, ponies don't just find out what their special talent is, rather, they develop it when they do something they like and really put their effort into it, thus ensuring every pony will be happy with his/her cutie mark. The marks often (but not always) fit their names because of outside influence, namely their families. For example, the Apple family have apple-related names and cutie marks, because they're from the beginning taught the apple farming trade and if the pony doesn't have anything in particular against doing that, they're likely to get an apple mark and continue the family business.

Cutie marks are meaningless.
A random symbol will appear on a pony's flank when that pony attains physical maturity, but that symbol has no meaning beyond what each pony chooses to ascribe it. For example, Cheerilee, in her lecture on cutie marks, tells her pupils that her own mark, three smiling daisies, represents her goal of helping her students bloom with knowledge, but she also says that she had already decided to become a teacher. If she had decided to become a gardener or florist, or any of a dozen other professions, might not the same mark have been just as appropriate? Or take Twilight Sparkle: her cutie mark is the exact same as Photo Finish's, yet in Twilight's case, it represents her affinity for magic, while in Photo Finish's, it represents a camera flash. Same symbol, wildly different meanings. Rainbow Dash's lightning bolt could just as easily be said to represent her job of manipulating the weather as her love for speed and racing. Many ponies may have decided to go into certain careers or pursue certain interests because of what their cutie marks were, instead of the other way around. In short, cutie marks have no meaning other than what a given pony chooses to assign it.
 * In "Cutie Pox," Apple Bloom gets a (false) Cutie Mark when she does a trick where, by spinning a metal ring around her tail really fast, allows her to fly like a helicopter. The Mark takes the form of a pair of grey disks with lines going down from the center. When she gets down, though, it is interpreted as meaning that she has skill at spinning plates. So Cutie Marks are at least somewhat up for interpretation0.

Ponies who've lost their way badly enough can lose their cutie marks.
Twist gains a cutie mark in "Call of the Cutie", but every time she's appeared afterward, she's been a blank flank again. Maybe she doubted her commitment to candy-making severely enough that she turned from that path, lost her purpose in life, and her cutie mark disappeared?
 * Wait, so even cannonically Twist is the worst pony?
 * Considering that Applebloom seemed to have completely dropped Twist as a friend ever since she initially got her Cutie Mark, one wonders if that may be the catalyst for losing her way, or even that she may be purposely suppressing it. Applebloom did seem to be poor Twist's one and only friend.
 * That could explain why that one farmer pony at the Grand Galloping Gala had no cutie mark - he can't have gone all that time without finding his special talent, could he?

The "Cutie Pox plague" mentioned in Twilight's book is the canon explanation for Story of the Blanks.
As read by Twilight, the Cutie Pox was a plague that caused ponies to suddenly get a bunch of cutie marks, and the ponies were forced to preform the talent each mark represents. If there was no known cure for it, and there were perhaps some bad marks as well that some ponies got, it's no wonder that in Story of the Blanks,.

Cutie Pox isn't normally very serious.
The text Twilight read said it went away as mysteriously as it first appeared, so no one really knew what was going on. However the text doesn't make it out to have been terminal. Applebloom however took a massive concentration of the flower that causes the effect, making her case that much more serious.

Cutie marks are implanted by the princess to take away free will
After unfairly getting rid of Discord and taking over Equestria, Celestia created the cutie mark system so ponies can't have unique personalities.
 * Huh... but the whole point of a cutie mark is to be unique sure, there are similar ones, or even repeats, but everypony assigns the meaning of them anyway.
 * What I meant was, when a pony finds anything they are good at when they are elementary school age the princess sends out a neutralizing cutie mark representing the talent, and it makes it so that is what they are supposed to do forever.
 * But when a pony gets a cutie mark, it doesn't make it so their cutie mark talent is the only thing they can do. Many of the ponies have talents other than their "special one", and there isn't anything to imply that the "special" one is the only one they can make a living off of. For example, Scootaloo's special talent is scooter stunts, (even if she doesn't know it yet, it is obvious) but she's also a good dancer. Fluttershy is good with animals, but she's also great at sewing. Applejack may work on a farm, but she's also shown to be athletic and good at sports.
 * Given that Discord seems intent on causing as much pain as possible to everypony he meets, it's hardly "unfair" to take the kingdom from him.

Ponies have potentially multiple Cutie Marks
Ponies don't have one "special talent". They have multiple talents, but the Cutie Mark simply represents the first one that is firmly expressed. That might explain why ponies might have talents that could not exist in previous eras (bowling, robots). Ponies are not limited to their Cutie Marks nor are their talents always thematically linked, but some might think they do.

A pony's "special talent" is actually two talents
Or, more specifically, a talent and a virtue. A pony has to discover both in order to get their cutie mark, but they only consciously recognize the talent.


 * Twilight Sparkle’s talent is magic, and her virtue is her dedication and discipline.
 * Pinkie Pie’s talent is throwing parties, and her virtue is her capacity for joy.
 * Applejack’s talent is running Sweet Apple Acres, and her virtue is being true to herself.
 * Rainbow Dash’s talent is flying, specifically flying with enough skill and speed to produce a sonic rainboom, and her virtue is her love for achieving the best she can.
 * Rarity’s talent is designing clothes, and her virtue is her ability to find the beauty in everything and share that beauty with others.
 * Fluttershy’s talent is her skill at working with animals, and her virtue is her patience and understanding.

A pony may discover their talent first, and then earn their cutie mark when they discover their virtue (like Rarity, who already wanted to be a fashionista, but had to find the beauty in a rock and share it with others at the school show), or they may discover their virtue and then their talent (like Twilight who was already dedicated, but had to realize her raw power), or they may discover both simultaneously (like Fluttershy who discovered her liking for animals and her ability to communicate with them all at once).

This is why the Cutie Mark Crusaders cannot earn their cutie marks. They already acknowledge their talents, but have not discovered their virtues. For example, Sweetie Belle knows that she is a talented singer, but will not be able to get a singing cutie mark until she realizes either how much singing means to her or how her singing can touch others.

Cutie Pox creates cutie marks based on jobs or activities that need doing.
Apple Bloom probably saw all those things out of the corner of her eye and her awareness of them unconsciously channeled her Cutie Pox into filling the criteria.
 * It would certainly explain why there just so happened to be a fencer in full dueling gear, a block of marble standing in the middle of town, and lions that needed taming...
 * What about the hula-hooping, plate-spinning, tap-dancing, and French-speaking? None of those were jobs that needed to be done.
 * Not every cutie mark pertains to a job. The hoop and the plates happened to be lying around, and tap-dancing and French-speaking were contingencies for when there aren't enough props around for tricks. Or you could chalk it up to Rule of Funny.
 * There was that tornado cutie mark though that had no purpose other than to force Apple Bloom to spin uncontrollably.
 * A limited form of wind-based magic, perhaps? A tornado could be really useful in a fight.

Even after death, afflicted ponies continue performing the talents associated with the marks until decomposition and general wear and tear degrade the body to an absolutely unusable state.

 * Nightmare Fuel
 * With serious potential for Black Comedy.

Adult ponies without cutie marks are seen as incredibly creepy, because they don't exist naturally
A cutie mark is what makes you individual. If you don't have one, you're either a soulless freak or just a foal. In dystopian cinema ponies have barcodes for cutie marks, clones have no cutie marks and ponies of mystery will not have them, ala The Blank.
 * So it's like Story of the Blanks?

It is traditional to suspend school for a day once someone gets their cutie mark.
Probably to increase confidence in the young filly by giving them a chance to show off in front of the entire class. Or because it's a good chance for a nice class activity. It's either this, or Cheerilee is a very laid-back teacher.
 * Alternately, Cheerilee had scheduled some physical exercise for later that afternoon, and when she saw Apple Bloom's new cutie mark, decided to leverage it into an earlier-than-planned workout.
 * Cheerilee is a child of the 80s, after all. Maybe it was nostalgia for her youth.