Shown Their Work / My Little Pony: Friendship Is Magic
Someone on staff knows their animals. Storyboardists Sabrina "Sibsy" Alberghetti and Raven Molisee attribute this to Lauren Faust; her series bible had both real horse pictures and anatomy next to her pony drawings to compare anatomy and how limbs and other parts would bend. The storyboardists also had similar pictures to work from. Lauren had insisted they avoid making the ponies perform actions that would be too much like a humans' action (bending a hoof like a hand, for example).
In many episodes (one of the more obvious examples is at Gummy's birthday party in "Party of One"), the ponies are shown shoving each other around with actions like headbutts and Ass Kicks, with the targets of these actions typically shrugging them off without so much as an annoyed look. This isn't Slapstick; Real Life horses are known for being very rambunctious when at play, which is why such roughhousing is sometimes called horseplay.
Horses will sometimes raise one of their front legs in a kicking motion when nervous, which is what Fluttershy does when she encounters Twilight Sparkle in the first episode.
Similarly, horses flick their tails in annoyance to shoo away flies and the like. You can see this happen several times in the series when a pony character is annoyed (e.g. Rainbow Dash looking non-nonplussed when the three bullies taunt her during "Sonic Rainboom".)
Twilight also uses her tail to swat at parasprites in "Swarm of the Century".
When Applejack pokes Big McIntosh in the ribs in "Applebuck Season" he responds by raising a haunch and glaring at her. That's an actual threat display by a horse about to kick.
The way the ponies move in general is very well done. When not being exaggerated for comedy, their joints bend in the same places and directions a real horse's would, and they have correctly animated gaits (walk, trot, canter, gallop) consistent with how fast they're moving.
The Ponies move their ears back and snort when angry or frightened, just like real horses do.
If pushed far enough, a disobedient horse will sit down on its rump and refuse to move, exactly like Pinkie does when she refuses to go with Rainbow Dash in "Party of One".
Fluttershy greeted the Manticore cat-style, leaning forward with her nose for a moment.
Sexual dimorphism is accurately depicted in Fluttershy's mallard friends.
The loon in Fluttershy's fantasy in "The Ticket Master" has a red outline on its eye. Red eyes are a distinguishing characteristic of loons.
Zecora's digging goes unexplained, but real zebras dig for water in the same fashion. The same behavior by a horse, however, is another threat display, so the scene actually makes MORE sense — Zecora was probably just nervous and a little thirsty, but the ponies around her misinterpreted her body language as grumpy and hostile.
In the episode "Dragonshy", Fluttershy is shown falling over stiff-leggedly with fear on several occasions... accompanied by the sound of a goat bleating. This may be a reference to fainting goats, a breed of goat which stiffens and falls over when startled.
In the song "The Art of the Dress" many references are made to actual equine anatomy...and then appropriate parts of the dress are shown being designed and constructed for them, making it clear the writers didn't just grab random words from a "Parts of the Horse" chart. "Parts of the Pony," by the way, would be an excellent song in MLP.
While Pinkie may be a little strange, in the episode "Feeling Pinkie Keen", she is shown rolling around in the grass. That's not her being strange; real horses and ponies will roll around in the grass like that.
Pinkie Pie removing wet pie filling from her face by covering it with molten chocolate, letting it dry and chipping it off is how some animals remove wet residues from their face using mud. The problem is, animals that usually do this are carnivores removing blood.
In "The Cutie Mark Chronicles", filly Fluttershy is drawn differently from most other fillies, having proportionally longer legs than her adult self. This is the correct body proportion for young equines. It also applies to other quadrupeds like deer and antelope, too. Other fillies were drawn in what would be more "human" baby proportions.
-It also is fairly common for future models to be exceptionally tall and gawky during their early teens. And Fluttershy does have, after all, ze magics.
In "The Return of Harmony Part 2", once the ponies capture brainwashed Rainbow Dash, she starts to snort and flare her nostrils, an activity consistent with real-life horses under duress. Earlier in the first part, a brainwashed Fluttershy swats Twilight with her tail, this is also something horses will do when particularly annoyed.
The ponies' mindsets are also very accurate. Horses are incredibly skittish creatures due to being a prey animal; as a result, they often freak out and panic at anything that frightens them, which shows up as background ponies freaking out.
Little Strongheart from "Over A Barrel" is the correct size and colour of a young buffalo.
In "Hearth's Warming Eve", when Princess Platinum, Chancellor Puddinghead, and Commander Hurricane grew impatient they began stamping their hooves on their ground just like real horses when they're annoyed.
The clicking noise Pinkie makes in "Baby Cakes" when she thinks Pound Cake has wandered off is a real sound that horses are trained to respond to.
The goats from "Putting Your Hoof Down" have oblong pupils, just like real goats.
In "MMMystery on the Friendship Express", Pinkie Pie scratches herself behind her ear like a dog. Actual ponies and foals will do this when they're young, but are unable to do this once they become fully grown adults.
From "The Cutie Pox": it's easy to miss, but every step of Twilight's buck when she dumps Spike (for a lame joke in a serious situation) is exactly how a real horse would dump it's rider, including her pinned ears and leading with her front legs first to put the "snap" into the whole motion.
As Fluttershy points out in "Tanks For the Memories", some species of tortoises do borrow into the ground and brumate for the winter. Plus Tank's digging motions when he prepares for brumation is accurate for real chelonians, including the pauses between strokes.
Those aren't Wimp Fights that the Cutie Map shows Twilight in the Crystal War timeline from "The Cutie Remark, Part 1". That's how horses really fight.
It could just be a coincidence, but it would appear◊ that potato chips and soda can indeed produce something that could be mistaken for a muffin. (The main problem in that picture seems to be the effects of the melted gummy worms.)
Applejack uses the correct game terminology while playing horseshoes with Rainbow Dash in "Fall Weather Friends".
Fluttershy's "freaky knowledge" of fashion when Rarity presses her for criticism.
Dragons are routinely shown hoarding treasure and eating gemstones. In many myths dragons ingest precious stones in order to fuel their fire.
A rock Rarity is looking at is broken by the effect of Rainbow Dash's Sonic Rainboom. In real life, sound waves can break rocks, and they've actually been used to break kidney stones. Also, the writers have shown their geology. Large rocks that are filled with gems when split open? They're called geodes.
A minor one, but in "Luna Eclipsed", Princess Luna speaks in the Majestic Plural.
The Windigos in "Hearth's Warming Eve" are represented with frightening accuracy as spirits of famine and cold that feed off hatred and in-fighting. The "famine and cold" part is correct, but many Wendigo myths involve cannibalism more than hatred and in-fighting. Though this could be Justified with it being a kids' show and all, despite what the fandom says.
One of Daring Do's nemeses is Ahuizotl, an authentic Aztec creature. Do they really expect kids to get these references?
In another mythology example: The first time Iron Will, who is a Minotaur, is encountered in a maze. In Greek mythology, the Minotaur lived in a maze constructed by Daedalus note of Icarus fame under the order of King Minos.
In Super Speedy Cider Squeezy 6000 they show a lot of work: Cider season is a very real thing and lasts only a few weeks; cider has no meaningful shelf life and so must be made fresh daily, the cider press shown is a real (and very old-fashioned) model, and the eponymous machine would indeed outperform the Apples' old method by about five to one, as claimed.
"The Lost Treasure of Griffonstone":
Griffons hoarding treasure makes a lot of sense, since the original griffon legends painted them as guardians of riches and rare artifacts.
Similarly, Arimaspi is based on a mythological race of one-eyed people who constantly feuded with griffons over the gold and treasures found in their northern homeland. The Idol of Boreas is named after the god of the North Wind, Boreas, who factors into this legend.
My Little Pony: Equestria Girls – Rainbow Rocks features the main characters playing instruments in a band. The staff went to great lengths to make sure they were accurately playing their instruments, from the right finger placements for guitar, bass and keyboards to proper technique on the drums. Even the character who plays the tambourine realistically twirls and tams it.