Twilight Sparkle had come to enjoy living in Ponyville. The close-knit community, hailed as one of the friendliest cities in Equestria, had taught her more about herself in a few years than the nearly twenty she'd spent growing up in Canterlot. The easy familiarity even for strangers was potent enough to power a wellspring of matchless magic and conquer the hearts of ancient evils. It had wormed its way into her own psyche, and she'd grown to know and love nearly every pony in town in one way or another, and her closest friends even more dearly. Her worries and stresses, however imposing, seemed just a little less insurmountable when she could call Ponyville home.
There was one dark corner of her soul, however, that knew the truth. The ponies of Ponyville were stupid, selfish, and forgetful. They abused the privileges afforded to them and thought nothing of dodging their sacred responsibilities. Their incompetence could only lead to chaos and ruin, the death of all the good in the world. They would ignorantly soak in their sins as Equestria crumbled around them.

The ponies of Ponyville never returned their books on time.

As a Librarian, Twilight Sparkle could not forgive that taboo. It irked and grated upon her, seeing ponies browsing the books, her books, when she well knew they still held a debt to the library. She felt a deep, spiritual pain when those same ponies would scoff or whimper or yell when told that they would have to square their accounts. A white hot ball of anger formed whenever they'd grumble and hem and haw about losing, losing, this book or that, and they'd look for it later, but needed to check out another right now.

Twilight had heard all the excuses. The library had been vacant for years, with no rules in place. The honor system was the right system for the right and honorable ponies of Ponyville. The books were old. The books were worn. My dog ate it. My husband ate it. A phoenix set it on fire. I lost it in the river. I was out of toilet paper. What's the big deal? Couldn't she just get more?

Ponyville's sole exception to this debauchery, its light in the darkness, was Pinkie Pie. Her pancreas did the Can-can whenever her library books needed returning, apparently.

No more. Twilight Sparkle knew that if she kept using a soft hoof, the ponies of Ponyville would never take their solemn duties seriously. But, she also determined, she was going to have fun with it.

Overdue.

There was a word to stoke the anger of any Librarian worth their salt. It certainly tweaked Twilight's bookish sensibilities in just the wrong way. But due to the incomprehensible wonders of language, it held more than one meaning. It tweaked Twilight's kinky sensibilities in an entirely different way.

The former meaning, of course, was simply the state of any book held past its required return to the library. An overdue book played havoc with the library's inventory and its availability to the public. Too many lost books, too many empty shelves, and a library could face closure. To Twilight Sparkle, it was the undeniable stench of failure.

The later meaning was a mare in an advanced state of pregnancy, her foal or foals grown enough to survive the outside world, but for whatever reason hadn't made their entrance. It tended to me no more than an annoyance for some mothers, tired of the process and eager to see their newborn colt or filly. To Twilight Sparkle, it was one of the pinnacles of a mare's attractiveness, delicious in all the major bodily changes and delightful sexual undertones. A certain sense of danger, that it could all come to an end at any time, added to the quandary that it somehow kept going, made a heady mixture for the unicorn's mind to digest.

There wasn't much use in highlighting the double meaning, but Twilight, in addition to being a librarian and a pervert, was also a wizard. Magic could be very sterile, clinical, and even logical on one hoof, with structure, language, and concrete cause and effect. One the other hoof, magic was clever, sneaking, and surprising, with applications and effects that seemed nonsensical and contrary until a pony discovered just what absurd rules it labored under.

It could be as mundane as substituting one word for another...

Rarity
Duchess & Dalliance: The Vamponies of East Riding
9 Days Overdue

Rarity was having a hell of a day. She was having a hell of a week. Orders for dresses kept coming in from Canterlot and Manehattan, and world of mouth seems to have garnered an interest from Las Pegasus as well. It was too good to be true, if only she could keep up. She viewed putting her customers on backorder as tantamount to a death sentence. Fashion could change faster than the seasons, and she was a unicorn who wanted to be avante garde, not merely contemporary. So, she kept working.
The fashionista thought she could rest when she finally had her foal. Maternity leave was a better excuse to take a break from the grind than demand outstripping supply. The only problem with that, though, was the foal herself. The little filly seemed stubbornly stuck in place, and had been for the last week. Nine days, Rarity reminded herself. A grand total of nine days since her due date, with nothing to show for it besides the puffed marshmallow she'd become. Every day just a little bit bigger. Every day her white coat just a little more pink as her poor stomach stretched. And every day, her mane and tail seemed to curl more tightly, defying all attempts at style. It seemed like the pregnancy had just flown by, without even time to plan a maternity line, but now every minute she was still pregnant seemed to drag on without end.
Rarity just felt too big. Small mercy that she only carried a single, but it was a big filly that had worn out its welcome. Her entire body felt pinched, pulled, and ready to blow, but somehow just never got around to doing it. She was tired, sore, angry, horny, hungry and wanted to cry. Some of the feelings came from obvious places, others from nowhere.
She wanted nothing more than to curl up in her bed, finally finish the book she'd been reading, and eat a whole tub of ice cream. Maybe by then, her pregnancy would get on with it. But with collection of unfinished clothing still strewn about her workshop, Rarity thought it could wait until later. There wasn't a lot she could do either way. So, she kept working.

Rainbow Dash
Daring Do: The Overmind's Crown
The Daring Do Trivia Companion
23 Days Overdue

Rainbow Dash could still fly. They'd have to cut her wings off to stop her from flying. But she handled about as well as a derailed Pony Express freightcar with a bumper crop from Sweet Apple Acres. It didn't at all stop her from doing her duty as a weatherpony, but it did change "in 10 second flat" into "when it gets done." Nurse Redheart had warned her about strenuous activity, but maintaining the weather was hardly strenuous for the best weatherpony in Equestria. In any case, it didn't seem like it was having any effect at all. She'd been waiting to see her awesome foals for an extra three weeks, but both of those oversized colts were still content to float around her belly like they owned the place. And every day, she felt a little larger. So while she could still fly, she more often reclined.
Being a pegasus brought with it one essential ability. Dash could reshape the clouds into anything she needed. Forming a perfect place to lay from fluffy, formless cumulus was a significant relief for a small pony far more pregnant than she had any business being. That relief had its limits, especially for a stuntmare that prized agility and speed. She was getting more than a little bored, but not even the odd loop-de-loop seemed to bring her closer to popping out her little ponies.
Dash rubbed her stomach, drum tight skin under the thin cyan coat, her hooves finding the odd bumps within the oblong sphere signifying a leg, a wing, or a head of her colts. "Come on, little dudes. Give mommy a break, okay?" she whined, feeling them kicking back after being disturbed. "I am just as awesome on the outside. So. Get. Out. Of. Mommy!" Tired desperation gave an edge to the plea, but Dash only received more kicks in response. They were staying.
Dash sighed and endeavored to nap despite the commotion in her midsection. She'd finish that Daring Do book if she could remember where she'd left it, but she was too big to feel like looking for it, and Twilight wasn't going to let her borrow something else...

Fluttershy
Duchess & Dalliance: The Mareseilles Menagerie
Flying Fit: A Pegasus Workout
27 Days Overdue

Applejack
A Guide to Jigs with Cedar Chip
2 Days Overdue

Fluttershy bit into her daisy sandwich with ravenous gusto. She could remember trying so hard to watch what she ate along with daily routines to keep herself in shape. Now, she could barely eat enough to stay full, and the only shape her body could manage was round. Her twin foals, and thus, their mother, were constantly hungry. But finishing the daisy sandwich didn't bring relief, just an uncomfortable fullness. The foals had grown so big that they were crowding Fluttershy's stomach, leaving little room for more food, no matter how hungry any of the trio was. The feeling would pass, and the starving mare would no doubt send in another sandwich.
Fluttershy was big. "Stupid big" as Rainbow Dash had said, though admitted that she was well on her way to being stupider and bigger herself. But where the size and its restrictions frustrated Dash, Fluttershy, actually, loved it. In a sense, she was the center of attention, and that would normally have sent the shy mare hiding behind the nearest tree. But in another sense, she wasn't the focus, her foals were. That slight shift made all the difference, and the mother-to-be would drink in the praise, amazement, disbelief, and all the other attention given to her gargantuan stomach and babies.
She wasn't at all bothered by her passing due date, nor the added size she accrued little by little as the days wore on. It was slightly concerning that she was still pregnant almost 4 weeks later, but Fluttershy was still enjoying every uncomfortable minute.
"Shoot," Applejack swore, shaking her head. "Ah fig're Redheart just ain't got our due dates right." The earth pony was just newly minted "overdue", but didn't seem convinced. She had a sizeable bump, plainly in an advanced state of pregnancy, but was adamant that she should be bigger. More visibly, the farmer's blonde mane and tail could have doubled in length from before, and she had them stuffed into messy, looping ponytails. "Prob'ly just run ragged. Seems like e'ry mare in Ponyville got all twitterpated at exactly the same time."
Applejack couldn't be far from the truth. The pair's waitress, a light blue Earth pony by the name of Dewdrop Plop had her own heavy, overstuffed belly, and did her level best to keep up with all the other hungry, pregnant customers at the Cafe Hay. Fluttershy had invited Applejack out to lunch to "celebrate", but was also using it as an excuse to chow down on food she didn't have to prepare herself. The yellow mare just nodded along, finding things to stuff into her mouth as fast as she could find the room.
Applejack had barely been affected by her own pregnancy, unlike Dash or Fluttershy herself, but always talked like she was disappointed it hadn't. "Ah fig're," the farmer continued, "Ah got at least another month. Ah dunno if'n you've got another month, but your due date just plain weren't right. Big as ya'll are, no sign o' birthin'?"
Fluttershy smiled and shook her head, pleased to inform anypony who asked how her pregnancy was progressing. "No, nothing yet," she said, standing slowly with a grunt, to let Applejack see her full profile. As tall and lanky as the Pegasus was, she couldn't help but be bulbous with an enormous colt and filly in her womb. Her wings couldn't find a good place to stay folded, the way her middle swelled out to the sides, and there was a constant, unconscious effort to realign them. "Twenty seven days, today, or... whenever you think..." she added, eager to divulge, but nevertheless more comfortable deferring.
Applejack whistled, "Well, lookin' good, Shy." She followed with a shrug, "Ah really couldn't tell ya. As long as y'all're doin' okay, best just to let things happen naturally. Ah'm just chewin' hay and spinnin' yarn 'til this little Apple's done bakin'."

Cheerilee
The Red Charger: Apple of My Eye - Book 2
Nice & Apple Spice: An Appleloosan Tale of Love
15 Days Overdue

Cheerilee plodded slowly into the library, gently opening the bottom half of the entrance door, and guiding her broad width through. She shut it behind her with just as much care. She was tired. The feeling rattled her very bones. But she needed to set a good example for her students, even when none of them were watching. Managing the excitable colts and fillies at the schoolhouse all day was one reason she was so very tired. The other was pair of colts she couldn't get rid of at the end of the day. They stuck with her, roughhousing without care inside her stomach, and blowing up their mother to the size of a schoolhouse. She was almost surprised she was still standing, at the same time wondering how she was still teaching a full day of classes. She'd been too big 15 days ago, and she's only gotten bigger since then, like her stubborn foals were ignoring the bell to recess. Her substitute also had the temerity to have gotten herself pregnant, so it was going to be a headache no matter how the situation played out.

Twilight Sparkle watched Cheerilee enter with deep interest. The schoolmare was overdue with twins, Twilight knew, because she had the library slips to prove it. Two overdue books translated into two overdue foals. She delighted in watching Cheerilee's swollen, burgundy belly sway with each of the mare's steps, and the exhausted grin given to her in greeting. Twilight noted, however, that Cheerilee had not brought any books to return.
The librarian could at least sympathize with Cheerilee's tastes. Big Mcintosh. Even if she wasn't in love with the stallion himself, she was at least in love with the idea of him. It didn't help that the Apple family was historically famous for turning out the largest, strongest, handsomest, and most virile stallions in Equestria. A hulking Apple was a suitor in many a bodice-ripping romance or hero of a fantasy adventure. A pony might be forgiven for thinking that the stories got exaggerated with each retelling, until they saw Mac himself and realized the stories were doing him a disservice.
The sympathies had to end there, Twilight thought. The schoolmare, of all ponies, should know to return her books on time.

Cheerilee filed up beside Twilight, spreading out her hooves to find a comfortable stance for her weight. The librarian returned a smile even before she'd said anything, "Hey, Twilight. How are you tonight?" she asked, her own smile tested by the colts tumbling in her cramped stomach.
The unicorn's eyes shifted to Cheerilee's stomach and back, "I'm doing well. How are you? You're still.... pregnant, I see," Twilight answered back awkwardly.
Cheerilee knew the Canterlot transplant wasn't the most social butterfly and had long come to accept her demeanor in these situations. And she was still very pregnant. The topic would force itself up one way or another. "I'm doing all right. Surviving. I know all about molding young ponies, so I thought I'd take my time with these two," she added with a strained giggle.
Twilight giggled back, which made Cheerilee feel better. "That is a good way to look at it," Twilight responded, her eyes shifting back to Cheerilee's middle, her cheeks flushed, "Looks like... looks like you're building them big..."
Cheerilee surprised herself by barking a laugh, then let the rest out gradually, "Oh.... you see that, do you? Go big or go home. I've been saying that since I was on the cheer squad!"
Twilight's eyes shifted away from Cheerilee entirely, and she stammered, "Well, it's a good... it looks... uh.... you look good."

What am I doing?
Twilight did have to ask herself that several times, her thoughts interrupted by a massively pregnant Cheerilee, skirt and pom poms, jumping frantically on the sidelines of her brain.
Just being friendly? Flirting? I don't think I've gotten to flirting yet. Should I be flirting?
It wasn't the first time she'd had this argument with herself since she'd started using her enchanted "OVERDUE" stamp. She wanted to inflict some kind of punishment on the perennially late ponies of Ponyville, and have some fun doing it, but she was having entirely too much fun.
It was unendurably exciting to see just how the glamour she'd placed on each overdue mare made them think about their predicament. The interplay of Ponyville's cursed dams as they reacted to one anothers' pregnancies was as fascinating as the triumphant spellcraft she'd weaved to make it happen. The daily recognition that those mares' bellies had grown just a little bit bigger, a little bit heavier. The constant conversation telling her just how pregnant they'd gotten. The humble, happy, and sometimes downright gleeful acceptance of their predicament.
Twilight's gaze was lured back to the bountiful Cheerilee, her deep purple cheeks still pulled into a goofy grin of laughter. Out of a million thoughts, her mouth managed to pull in only the most embarrassing, "You look great big... pregnant. I mean... you look great all... big and pregnant like that..."
Stop it.
"What.... what can I do for you?" Twilight resumed, but knew she'd given way too much away with the deepening amusement on Cheerilee's face.

Oh my, Cheerilee thought, stifling the fit of giggles threatening to break out.
Someone has a thing. A fine time for it in Ponyville, most definitely. Or if not that, some librarian is deeply jealous that's she's been left out. She didn't want to tease the poor mare. That kind of information was hard for any pony to reveal, not least of all a notorious shut-in, an not accidentally. But that made it no less amusing.
Cheerilee tamped down on her sense of humor, cleared her voice, and stated her original reason for coming to the library. "Twilight, can I get another book?"
Before Twilight could answer, the teacher interrupted, "I know, I've already got two books out, but I want something to read until the foals get here. As... uhm... great, big and pregnant... as I am, I really can't turn my house upside down looking for lost books."
Twilight looked torn, but Cheerilee powered through as if Twilight were a student failing to spell a word correctly, "I know, why don't you come back to my place and give me some help..."

Author's Note

1) This isn't exactly canon, even for a smutty fanfic about small magical talking horses. It is the direction I was planning to take things, but the little prompts I had seemed to fit together well enough to make a chapter. Better than writer's block.
2) In the event I expand any of them, they may not occur at the same time, or in the same order. It may not even be Cheerilee! She just fit well.
3) This is the same Twilight that brainwashed an entire town to want her ratty old doll for a homework assignment, and was powerful enough to both accidentally alter her friends' fate and fix it after she realized her mistake. This does not make you an Alicorn, just psychotically insane on one level or another.