So you're writing a story with an all-OC cast, and maybe you decide to have it set in the future. Maybe you decide to make it about space-faring ponies on a distant planet, and maybe you have the princesses be long-dead and give your fic a tone – be it grimdark, solemn, sad or darkly humourous – that doesn't quite mesh with the tone of the show. All of a sudden, you type "hand" instead of "hoof" and suddenly you realise that hey, your story may as well be an original piece of fiction about humans (or some alien species of your own creation).

I firmly believe that a work of fanfiction must be enriched by being based on what it's been based on. If you keep too little of the source material's elements and flavour, your story might actually be damaged by being tied to the canon of that source material.

But how much pony is too little pony? As a writer of stories that mostly have OCs, this is something I'm always worried about – writing about my own characters may cause me to slip off the slippery slope of fanfiction and write something that's about ponies in only the most cursory, on-the-surface sense. I don't want to do that.

What are the key tenants of MLP? I think the key to writing something that's "pony enough" is to try to capture that positivity and belief in the power of friendship that the show has. Fallout Equestria, for all its OCs and grimdark, makes it very clear that Littlepip needs her friends to accomplish her goals and that the actual show's values are vital to rebuilding Equestria.

On the subject of OCs: what makes a character a pony rather than a human you're calling a pony? I'm aware that in all writing, regardless of whether it's about ponies, or rabbits or aliens, we're actually writing about humans, but still: what do you think are the key differences between a pony and a human? What about they way that they enter the world and live in it is different to the way we do, and how does that shape their personalities?

Is this something that concerns anypony else?

My fiction is mostly everything you have put up. Future, aliens attacking, mane 6 long dead, OC ponies, griffins, zebras, buffalo, dragons, no human (but maybe will be mentioned), leting the readers join in the battle. I think I got everything you put up. When it comes to friendship I can only say teamwork. And some side romance. I have many OC for this war but few have joined.

Huh. You made the reference. I never would have expected that in a conversation about mantaining ponyness.

In any event, I have always felt that the true way of maintining that pony feel was to resist the urge to impose the more human developments such as extremely advanced weapons and painfully unfair systems like fascism and objectivism. As well, it is important to bring ponies to the edge but always yank them back with a vengeance. Don't even let them stare into the abyss. But they can freely battle monsters, because another facet of ponyness is the capacity to do that while not becoming monsters.

I have the idea for a future-set story about the limits of how far a pony can go in order to reset the world to the Equestria we know and love, when the world itself has forgotten what that even means. Could an absolute Emperor return a sugarbowl principality and still be a citizen of it after all is said and done? I like to think so.

In my opinion, the best way to retain 'ponyness' is simply just to reference their differences from us, but subtly enough that it doesn't railroad all over the reader. Kkat preserved it well despite the radically different atmosphere and tone as opposed to the show, because she kept consistent with idioms, casual use of equine physiology, not being able to fire with anything but mouth or magic, etc. It felt natural to read, but still constantly reminded you that these are ponies. This technique can smooth over any concerns of the far future or grimdark fics.

'It's all in the presentation', as Rarity would say. Make it casual, but constantly have little words here and there that prick the reader into envisioning your characters are the colorful ponies we so enjoy.

The second 'must have' is references to the show, whether through locations or characters we've seen and heard from there. A connection to canon is all but required and will pull in more viewers than if you just had it totally separate from the show. Kkat showed another example of this through OCs who had interacted with the characters either far in the past or through memory orbs, which forms an attachment and grounds the fic as 'pony'.

If your writing doesn't have both of these, you're not really writing ponyfic so much as an original fiction that happens to have ponies in it - there is a distinction there - or just a bad fic in general.

Someone named EustatianWings had some neat pointers on who ponies are and how they think (source).

They're really big on the whole "special talent" thing. Their females tend to lead, while their military is mostly males, so we can say their gender roles are different. They're more likely to flee than fight. They don't have as much respect for predatory animals, seeing them as monsters rather than hunters. They need a high-fiber diet and can eat the paper off of a carton of ice cream if they want. They prefer small business and hoof-made things to large brands and mass production. They have electricity, but no mass media. They have less need for respect, more for leadership. They grow up faster, but don't rush to prove themselves "real adults." They have no nudity taboo. They sit on piles of straw and eat the flowers off the table in restaurants. They're, you know, ponies. Most of this is well-supported "canon," too.