Horsing Around

"Riding is the only thing a King learns how to do right, since a horse is no courtier and will just as soon throw a Prince as a stable boy."

Horses can be real bastards. Tensing up as you fasten a saddle only to relax and leave the rider upside down, biting hands, "spooking" and riding off with their rider, kicking anyone stupid enough to get south of their arses, and if they lie down suddenly... get off quick, they're about to roll. And as for camels...

Horses, both in fiction and real life, are living creatures, and come with their own personalities. They lose their tempers, they get scared, they react like you'd expect an animal to react. Often suspiciously like you would expect a dog to react. Sapient Steeds are liable to be this if you treat them badly... or possibly just because, like humans, they have a mischievous streak. And lord help you if you have a Moody Mount.

Aversion of Automaton Horses, and in the case of wild horses of All Animals Are Domesticated. Also an aversion of horses' usual Animal Stereotype of being noble, loyal and steadfast.

Examples of Horsing Around include:

Comic Books

Jolly Jumper, the horse of Lucky Luke, is a textbook example. Besides being able to run impossibly fast and long, even while sleeping, and always coming when Lucky Luke whistles, as the series develops he gets the ability to speak and play Chess with Lucky Luke. Oh, and don't think of stealing him. It will get really painful, when he recognises that you are not his rider.

Film

The scene in the Pecos Bill segment of Disney's Melody Time where Slue-Foot Sue tries to ride Pecos' horse Widowmaker. Watch it here, starting at 4:00.
Pegasus on Hercules is usually gentle with Herc. Megara, on the other hand...
The Prince's horse in Sleeping Beauty, who until the climactic scene was very stubborn and had to be bribed by carrots to do his master's bidding, and even then the horse bungles it and charges straight into a puddle.
Phoebus' horse from The Hunchback of Notre Dame when he was told to "sit". His face seemed well smug. Self-satified maybe?
- Disney in general seems in love with this trope. Horses acting up are, of course, a good way of getting laughs out of parents and children alike.
In Spirit: Stallion of the Cimarron has an entire sequence where soldiers attempt to "break" the resistant Title Character. Fittingly enough, the background music is "Get off of my Back." Later in the movie, Spirit is just as resistant and rebellious to a kinder Native American, but eventually warms up to him.
- Horsey people in general tend to have a Misaimed Fandom towards Spirit considering he's unrideable.
Maximus from Disney's Tangled pulls this when Flynn tries to ride him near the start of the movie.
In The Mask of Zorro Alejandro tries to summon his horse, Tornado, with a whistle, so he can jump out of a window onto its back. The horse comes at the whistle, but is having none of this "leaping onto his back" stuff, and steps aside, causing Alejandro to land with a painful set of Amusing Injuries. This is also a throwback to an earlier scene where the previous Zorro did it without a hitch.
The horse ridden by Chon Wang in Shanghai Noon has a mind of its own and rarely responds to his wishes unless it wants to.
Seabiscuit in the film and in real life.
In the third Teenage Mutant Ninja Turtles movie, the Turtles try their hand at horseback riding. They are each in turn thrown off...except for Leonardo, who goes riding off standing on the horse.

Literature

In Black Beauty, a horse revolts when the bearing reins are drawn too tight to bear. As the book is an Author Tract against cruelty to animals, the narrative's sympathy is entirely on the side of the horse, with the result that bearing reins soon fell out of favour except as safety equipment.
In The Elenium novels, Sir Sparhawk's horse Faran. Faran is infamous for his bad temper and a tendency to bite strangers (such that Sparhawk always has to warn handlers about it). In one of the later books, the child-goddess Aphrael tells Sparhawk that Faran only has a bad temper because he is trying to please Sparhawk by matching his personality. Much to Sparhawk's annoyance, Faran has a habit of prancing whenever Sparhawk rides him with his formal armour on. The horse is also remarked upon to be unusually intelligent, to the point of understanding Sparhawk's speech and having memorized the ritual entry into a Pandion Chapterhouse as well as Sparhawk has.
The horses of Tortall have very distinct personalities in general, but special mention goes to Cloud (Daine's pony, and often a grumpy, motherly Lancer as well) and Peachblossom, Kel's inappropriately named, bad-tempered gelding, who decides to be Kel's equine partner because she treated him well and because (as he tells Daine) she needs to be looked after.
Several novels in the Heralds of Valdemar series include (usually humorous) antics from horses, such as the infamously ugly and ill-tempered Grey Stud in The Last Herald-Mage, a beautiful but stupid horse in Oathbreakers, and an entire stable full of misbehaving horses in the short story "Spring Plowing at Forst Reach" in Oathblood.
- Multiple Companions are described in passing as doing this as well, either due to disagreements with their Chosen or a taste for low humor. Companion Kalira once saved her Herald from a woman pulling a Wounded Gazelle Gambit, commenting "I wish I'd had something to leave on her shoes!"
The horses in the Hank the Cowdog series are real jerks because, as Hank puts it, not only do they think they're better than everybody else, but they will go out of their way to try and prove it.

Hank: If there's anything worse than pretense, it's reality. And anything that weighs 2000 pounds and bites and kicks and stomps must be considered reality.

The protagonist of the Garrett P.I. novels dislikes horses, and claims they're sneaky bastards that invoke this trope on him deliberately every chance they get.
The Chronicles of Narnia novel The Horse and His Boy has a Deadpan Snarker of a horse as a main character.
Boris from Going Postal is a half-mad stallion who would have been a perfect race-horse if it weren't for his tendency to throw and trample the jockey, attack the other horses, then jump the fence at the first turn and bolt. Moist von Lipwig asked for a horse with "a bit of fizz, and not some feagued-up old screw", and Willie Hobson gave him Boris to ride. So what does Moist do? Raise the stakes by riding Boris bare-back from Ankh-Morpork to Sto Helit.
Runaway Radish from the children's book of the same name is described as a good bad pony, because he teaches his riders to make sure they check their girths, latch his stall, close all gates, plug in the electric fence, tie tight knots... and hold on tight!

Newspaper Comics

Lucy the pony from Non Sequitur is unusual in that as a talking horse she'll actually explain why she's acting spooky or headstrong.

Video Games

Averted in The Legend of Zelda: Ocarina of Time. Epona is a trusted horse that follows the player any time she is summoned.
- However, unless you learned 'Epona's Song' from Malon in the pre-Ganon Hyrule, Epona won't let you ride her. When you beat Ingo in a race with her, the rancher is utterly flummoxed that anyone could 'tame that wild horse.'
In Red Dead Redemption, if you spur the horse you're riding too much, it will throw you.

Western Animation

Appa of Avatar: The Last Airbender.
The Classic Disney Short How To Ride A Horse is built entirely on this trope. Note that Walt Disney (and a lot of his animators) were avid polo players.
My Little Pony Friendship Is Magic usually averts this when dragon cub Spike rides on Twilight Sparkle's back, (justified in that they communicate verbally and Twilight's like a mother to Spike) but a parodical version of this trope shows up in "A Dog And Pony Show" when the dogs are trying to grab onto the ponies, who in turn jump around and knock them off like very disobedient horses.
- A loose example that's played for laughs in "The Best Night Ever." Two stallions help to pull the ladies' carriage, and glare angrily at Spike when he whips them - horses in this world are stand-ins for sentient human beings, not beasts.
- Pony on pony action (no, not porn) usually results in at best a miffed pony. Rainbow is less than happy with Applejack rigging her with a crude bit and bridle for aerial assault in 'Bridle Gossip', and even Twilight lets out a miffed reply when Spike tries to have his 'noble steed' (read: her) charge. And 'Clover the Clever' (played by Twilight) is sullen about having 'Princess Platinum' (played by Rarity) ride her to avoid wading in a stream in the Hearth's Warming Eve play.
- Spike also gets thrown off by Applejack and Rainbow Dash during a rodeo in "Fall Weather Friends." (One wonders how they talked him into participating in the first place.)
- Twilight also flips Spike off her back for making a lame joke in "The Cutie Pox".

Real Life

Truth in Television since horses are still animals. Very big, powerful animals. Aside from the obvious danger of a kick or a nasty bite (which can be severe enough to disable or even kill), some horses can have a nasty habit of lying down suddenly when you're riding them... to roll in the grass while you're still on them. The results can be fatal. So if your horse goes down suddenly... get off the horse immediately! (especially if he's in water.) They can also spook or bolt if they're stung or startled, leaping or galloping off in a panic. When that happens, getting dumped is almost inevitable.
Beyond this, they can be sneaky devils as well. A common one is them breathing in as you fasten their saddles, so that when they breathe out again... the saddle becomes loose and you end up riding upside down. They have lots of tricks beyond this... like getting the bit anywhere it's not supposed to be (between their teeth, beneath their tongue, back in their mouth etc.) and flatly refusing to follow anything the rider asks of them.
- As an old refrain says "Mas sabe el burro que quien lo monta" ("More knows the donkey than the person that's riding him"). Well, horse.
- And the worst part of all this? If a horse decides he isn't going anywhere, that horse - well - isn't going anywhere. There is a reason no trained equestrian gets in a tug-of-war with a horse - they have the experience to know they won't win. Horses are best managed by kindness and trust. Failing that, they are managed by manipulation, followed shortly by bribery. When that fails, the rider in question calls in someone with more experience.
Horses will not jump anything unless they are a) in a blind panic or b) being ridden by a competent rider, There's an old saying that you can fool your enemies, fool your friends and even fool yourself, but you can't fool a horse and if you don't know what you're doing you probably will make it past the first jump.... about ten feet past, depending upon terrain and atmospheric conditions. The horse, on the other hand...
Then there are ponies, who, in addition to all of the above, often have very talented lips, and easily master the art of unbolting their stalls. And occasionally every other stall in the barn as well. If horses are troublemakers, ponies are Dennis the Menace.
Donkeys the close relative of horses and ponies are well known for their stubborn nature and tend to be less trusting towards humans. However, they are also highly intelligent and dependable if you earn their trust.
Likewise mules (a cross between a male donkey and a female horse) tend to inherit the stubborn streak of their donkey fathers hence the phrase "stubborn as a mule". But are quite dependable, hardy, and intelligent even more so then either parent. Ticking them off is not wise due to fact they can strike with their hooves in any direction, even sideways.
- Hinnys (a cross between a female donkey and a male horse) are similar in personality to mules but are much rarer due to difficulties in reproducing them.
Camels are also known for behaving badly; they'll spit, bite, refuse to move, or run out of control for seemingly no reason. Balanced by the fact that in the desert you'd still rather have a live camel with you than a dead horse.
- If you were a camel and some nasty fellow wanted to make you carry his merchandise through the desert and then take all the profit for himself wouldn't you want to spit at him, bite him, refuse to move when he said, or run out of control?
Famous racehorse Seabiscuit's quirks were actually toned down for the movie, and he was a notorious bad actor until he was just lucky enough to get an owner, trainer and jockey who understood him. The race instructions "...never hit him with the whip, only touch him with it on the left side, and never more than three times..." were taken word for word from an interview with the real Red Pollard.
There was an attempt to domesticate zebras during the colonial era due to them being immune to diseases that were decimating horses. They proved to be too prone to panicking and, being wild animals, were much more unpredictable than horses. A few people had succeeded, but generally it considered too much effort and the project was abandoned.