It was great. She was here, he was ready, and I was gonna get away with murder. Of course I had his foal in me at the time. Little Windstorm enthusiastically pumped his semen into my cunt as I held him and told him what a good job he was doing. He definitely had enough to impregnate somepony, and he was totally into it. Every time I babysat, we’d go up into his room, and get him mounted on me right away. I had to lay on his bed of course, but the colt didn’t mind, and was soon lustily thrusting away like he was born to be inside me.

He didn’t ejaculate at first, just had a look of unparalleled wonder as his adorable dick started pulsing inside me. “What was…?” he said looking down at me in absolute amazement.

“That happens to you every time you do this,” I told him in drunken pleasure, “I’ll let you do it whenever you want. Just thrust your penis in me until it happens again.”

“A-again? That felt really …good!” he said hopefully, sliding right out of my wet pussy.

“Give it a rest,” I told him, “When you start feeling achy for it again, let me know and we’ll get you thrusting in me right away.”

After the third time, he hugged my torso with his nose buried in my chest fur as his hips humped deep and throb, throb, throbbed in there. “You’re the best babysitter ever,” he said with a happy sigh.

“I know,” I told him smugly, “So wanna go play video games now.”

His ejaculation started to pick up, thrillingly. He tensed as he started spurting into me with strong jerks of his penis, then said “S-something came out!”

“You’re making semen now,” I told him with a rush of lust in my heart. “Your penis squirted semen right up into my vagina.”

“I-is that good?” he asked uncertainly.

“Yeah,” I told him, “I’m gonna keep your semen inside me now, all day, until you’re ready to put more into me. That’s why your penis jerks, because it’s trying to pump semen into me. And now you’re old enough that you can.”

He pumped more and more semen into me over the year. I showed him once, having him pull out, and licking my own vaginal juices off his surprisingly large erection, until the colt climaxed, and ropes of white seed shot out of his penis. “That’s what you’re putting into me,” I told the climaxing colt, letting the semen land right on top of me. “Every time you do it.”

“I… I wanna pump it all out my…” he said lustily, flexing his penis against my cheek. “Ohh, I wish I could do more!” he exclaimed, frustrated.

“Just give it a rest, your body needs to make more semen first,” I told him in amusement, “When you start wanting to put it in a filly again, that means you’re ready, and next time you can squirt every drop into me.”

“I… I wanna,” he said dizzily, hugging against me.

So he was thoroughly ready to have sex, and when I didn’t go into estrus that year, I knew exactly what I was gonna do.

“Pleased to meet you Teadrop,” I told the little pegasus filly, well, not too little. She was smelling of estrus, her very first, and she wasn’t even supposed to leave her house. Fucking assholes of parents didn’t want to stop her from doing what’s natural.

Well, I wasn’t gonna do what’s natural either, but I wasn’t gonna stop her. I was gonna start her. “I’m Candy Kiss, Windstorm’s babysitter, and I let him get away with all sorts of naughty but fun things.”

“Like what?” she asked, ear quirked in attention.

“Like this,” I said, laying back and spreading my legs. “Have you ever touched your fillyhood before?” I start rubbing a sensuous hoof between my legs as she stares, big-eyed.

“You haven’t, huh?” I ask slyly, as she blinks and blurts out,

“N-no. We’re not supposed to touch there.”

“Well I’m touching there,” I tell her teasingly, “And you can too if you want, you won’t get in trouble. It feels really good.”

She doesn’t last long. Soon she’s there, rubbing herself just like I am. “I think it does feel good!” she exclaims in surprise. “It’s all tingly.”

“Great!” I reply, looking between her soft blue furred legs with interest, “Are you getting wet down there, yet?”

“I… uh” she says, lifting her hoof and looking at it, “Yeah, I guess…?”

She goes back to rubbing herself as I say, “Fillies start to get wet down there. Your body’s making a special fluid that starts coming out of you a little. It’s really slippery. Feels kind of like you’re melting inside.”

“Y-yeah, wow… I think it’s coming out of me,” she says in shock.

“Well, keep at it, and I’m gonna go get Windstream, so you can use your wetness to make him feel good too,” I tell her, as the filly blushes and starts to close her legs.

“Don’t worry, he knows all about this stuff,” I assure her, “Let’s all get together and just touch ourselves.”

I have to lead again, but soon Windstream and Teadrop are both caught up in masturbating. “Keep touching yourself,” I urge her, “But look, his penis is coming out.”

“It… wow it is,” Teadrop says distantly, looking at the colt’s swelling erection, “Are you gonna pee, Windstream?”

“No, it’s for something else,” I tell her before he speaks, “Just watch, and see what happens to his penis.

After a while, Teadrop huffs, “Wow, it’s getting… really big,” staring at that colt’s penis while humping against her own hoof.

“I wanna put it in, miss Kiss,” Windstream whines, erection straining against his crooked hoof.

“I think you two are ready,” I announce, “Stand up, Teadrop. This is gonna be awesome.”

She does, looking up at me, and I say, “Point your butt right at Windstream and turn your tail aside. Really show him what you’ve been touching.”

“But I don’t have a penis or anything,” She says uncertainly.

“You have a vagina,” I tell her, “It doesn’t stick out, but he still thinks it’s really beautiful. Right Windstream?”

“Yeah I… I like vaginas!” he says eagerly, standing himself as his erection bobs underneath him.

Teadrop presents for him, and looks back cooing nervously, “Y-you like this, huh?”

“Yeah,” he says, staring fascinated at it. “I’m gonna…”

“Go ahead, Windstream,” I tell him amiably, “Just like we practiced.”

As he grabs and mounts the surprised Teadrop, I tell her, “He really wants to do this. Boys love getting up on your rump like that.”

“I-it’s okay?” she asks anxiously, looking at me with a solid blush.

“You look beautiful right now,” I tell her, “The best most wonderful fillies let a colt hold their butt like this. You’re doing a really good job.”

“Just… stand here?” she asks lamely, “He’s—” her eyes narrow.

“That’s his penis,” I tell her smugly, “It fits right against you back there, doesn’t it?”

“It… he’s gonna rub me with it?” she asks, staring forward distantly, “He’s really rubbing it and… w-wait…” The filly gives these cute little choked gasps as Windstream penetrates her. He starts fucking her right away, as I tell her,

“Feels good, doesn’t it? That’s a penis sliding in and out of you. See why you had to get wet, now? You’re nice and slippery inside. And really hot.”

“I… I… this is… okay?” she asks rocking back against the thrusting.

“Just enjoy, filly,” I tell her frankly, “You don’t wanna do anything other than let him thrust his penis in you now. He feels the same way. He’s gonna keep pushing it deep, and he’s not gonna stop.”

“He’s… not… gonna…” her words fall to a moan, as she stares forward, mating with him like the animals they’ve become.

She looks back in surprise when he hauls up into her and suddenly stops, but only a moment, before she snaps to staring forward again, sucking in astonished breaths.

“How do you like Windjammer’s semen?” I ask her happily, “It’s coming out of the tip of his penis right now, squirting deep into you.”

“It’s… hot and… ungh…” the lust-ridden filly pushes her rump up against Windjammers, as his seed starts to leak out of her little cunny and puddle between her legs on the floor.

“You’re full of semen now,” I tell her eagerly, “He squirted it into your vagina, and way up into your womb.”

“D-deep… he squirted it deep!” the filly gasps.

“That’s not even the best part,” I say smugly, “He’s gonna finish you now with his tongue.”

She looks confused at that, as Windjammer dismounts, stammering, “I-I swear I like it. Your b-bottom is a thing colts like a-and I’m a colt so don’t worry oh my semen’s coming…” he stares between the filly’s legs, “Out of you…”

Then Teadrop gets to stand there gasping in shock as her new coltfriend pushes his own semen back in, stimulating the filly more and more, until she cries out in purest utter delight, “I love your semen inside me, Windjammer!”

“He feels like this too,” I say grabbing her attention again, “It just builds and builds higher until it fills him up like lightning and then he explodes. Can you feel that happening to you?”

“I… I…” she pants, staring forward with half lidded eyes.

“When it happens to him, that’s when he starts putting semen into you. The semen starts squirting out of his penis, over and over, and he can’t stop doing it. How do you think it’s gonna happen to you?”

“I… I don’t… hunh it keeps… getting bigger~!” she whines in distress.

“It’s okay filly, just…” I say, stroking her mane and getting nose to nose with her, “Let it happen. "How is it feeling right now?”

“I can’t it’s… bigger and… it’s so tingly my whole… body I…” she says, gulping in air, “It’s… filling me up! I—I can’t…! I…!”

“It’s happening to you, huh?” I ask the filly whose pupils are shrinking in shock, “Filling you up with lightning. You feel like you’re gonna do something, like something’s gonna happen. Then… you can’t stop.”

She squeals in surprise as her orgasm hits, shuddering in place as her cunny starts rhythmically clenching. I lay my head over hers, the orgasming filly’s skin hot against mine, as she gasps, “Thank you…! Oh… thank you… oh…”

You better bet that eleven months later, she’s gonna be squeezing his foal out her cunt with her gigantic belly. After that experience, the horny filly took every opportunity to sneak out of her bedroom and hurry over to my place, when she knew Windjammer was gonna be waiting there for her.

“Ohhh I really feel it,” the winking filly related, as she turns, wings spread, tail lifted, panting as she watches the colt approach, then climb on her rump. She stares forward then, giving a relieved sigh as he mounts her and begins thrusting. I wait until the foals have that dull eyed look of two ponies thinking about nothing but mating, climax and ejaculation. Then I say,

“I think it’s about time I told you what semen does.”

“What?” Teadrop says breathlessly, looking at me in confusion.

“I have a foal in my belly,” I tell her eagerly, “My womb inside my belly is getting bigger every day. My whole body’s changing to grow the foal inside me and nourish it. I’m gonna be making milk, and… and giving birth. I–I’m turning into a mommy, just like your mommy. It just started growing in me one day, and I started changing inside, and do you know what did it?”

“No, what?” the filly asks in understandable concern. Windjammer has also stopped thrusting, hugging the filly’s hips, trembling with need as he still looks at me with burning curiosity.

“Semen,” I tell her with a smug grin, “Windjammer pumped his semen into me, and it swam right up to my egg, and turned it into a foal. The little tiny thing attached to me in there, and now it’s growing and changing me into a mommy.”

“Y-your egg?” Windjammer asked uncertainly.

“Every female makes eggs inside her,” I say in a practical tone, “She can tell when she’s made an egg in there, because she goes into something called estrus.”

“But I’m in estrus!” Teadrop said in shock.

“Yup,” I say in terrible amusement, “His semen’s swimming right up to your egg right now, and soon you’re gonna be turning into a mommy.”

“But I’m just a filly!”

“A filly in her first estrus. Estrus is how you know you’re gonna have a baby in your belly, no matter how old you are.”

Blushing in frustration, the filly says, “Well I don’t wanna baby in my belly.”

“If you don’t want a baby in your belly,” I tell her, unconvinced, “All you have to do is take his penis out, and not ever put it inside you, even when you want it. But I think you want a baby.”

“N-no I—” the blushing filly attempts, as I tell her smoothly,

“Imagine your belly getting big and round, and stiff. Imagine it clenching hard, over and over again, pushing a baby pony through your vagina. Right where Windjammer’s penis is right now, that’s where your baby comes out. Right… here,” I turn and present for her, showing her my quiescent snatch. “You’re gonna stre-e-etch open,” I say, pulling a buttock to spread myself, “It’ll come outta you like a tube of toothpaste. And all you gotta do is let him put his semen inside.”

The filly’s eyelids droop, her staring forward at nothing, as I tell her, “Imagine his semen bursting into you, filling you, changing you. You’re gonna let it happen because it feels too good to stop.”

Windjammer starts thrusting again, bless his soul, I tell the overwhelmed filly, “You’re not even Teacup anymore. You’re just a filly with a vagina, who needs to start making a baby inside her. Windjammer’s not thinking of anything but cumming inside you, because he’s a colt, and you can feel his penis.”

“But… I… I… I… hnh hnh hnh,” the filly tried to protest, until she was just grunting and thrusting along with Windjammer’s energetic thrusts of his thick cock.

“That’s it. Let it take you over,” I tell her, “The need to feel his penis doing it in you. You’re melting around him, stretching. You’re getting ready to grow a baby inside you. He’s changing too. Windy’s so erect right now, it’s aching to cum in you. Every time he thinks about you lying there, squeezing your belly down, while a foal slides out between your legs, it makes him wanna do it more. He wants to make you do that. He wants to put a baby in you.”

“I… I…” Windjammer says desperately, “I’m getting… ready to… put a baby in h-her. I don’t… care I wanna… pump in you, Teacup, wanna make it bigger and… annd it’s… g-gonna squirt in you it’s… it’s…!”

As Windjammer tenses in the unmistakable throes of his sensitive climax, I tell the colt cooly, “That’s right, you’re putting a baby in her now.”

“Hnnh!” Windjammer exclaims urgently, as the filly squeals and pushes back against his groin.

“Get it deep inside you, Teacup,” I advise the incensed filly, “Those squirts are changing you into a mommy. You’re making a foal in your belly now. His semen is making you do it.”

Teacup’s just staring forward moaning senselessly at this point, a deep, panting, “Huhh… huhhh… huuh…!”

“S-she started… cumming,” Windjammer says shyly, holding himself firmly in the filly while Teacup trembles there, stiff-legged underneath him.

I cup my neck around Teacup’s in response, murmuring, “It’s okay, just do what your body needs to do.”

Finally Teacup’s done, and Windjammer pulls out, whereupon she sinks to her squishy haunches in shock. “It’s a lot more powerful when you’re thinking of a baby growing in you, huh,” I tell her somewhat sympathetically.

“I… I don’t know what to think,” she says faintly, “I never thought…”

“It’s okay, just let it happen for a while,” I tell her warmly, “It’s what your body wants to do right now, so let it do its thing. See what it feels like to turn into a mommy. You’re naturally a mommy like every other filly, with everything already inside you, ready to grow a foal. It’s been growing in you your whole foalhood, and now it’s gonna… wake up I guess you’d say.”

“What do I do?” she asks tearfully, “I feel like… I-I’m changing!”

“It’ll take a long time,” I assure her, “Lemme know when you start getting sore teats, because that means you’re gonna make milk, kind of like a cow but not as much. One day you’re gonna start showing, with a little bulge in your belly. Your parents won’t even notice though, because you’re just gonna let it get a little big. Then I have a…” dark ritual “…fun activity that we can do, and you’ll be back to normal again.”

She doesn’t seem mollified, so I add, “It won’t even start showing until winter at least. Until like Hearth’s Warming you’re just gonna be a little hungrier and maybe more tired than usual. Growing a foal is hard work, and it’s not something you can exactly take a break on.”

Well, except that one mare “Bumpy Wish,” who let her foal get so big it was almost ready to come out, then she paused its development, because… she just liked having a big belly with a foal in it. She’s been pregnant for years now, and her foal doesn’t even think she’s a foal anymore, just like a…second Bumpy Wish, who shares a big, pregnant body with her mother. I think she can… take over or something? Veto some actions? I don’t know the details.

Well, whatever. Sure she’s forcing a foal to stay in her belly, but it’s not any more cruel than forcing a foal to be born. Long as it works for them, I’m okay with it.

“But it’s still totally awesome,” I tell her, sitting beside the filly, “We’re both gonna get to see our bellies growing bigger with the foal inside us. Sorry to surprise you, but you shoulda seen the look on your face. Priceless. Look, if it gets to be too much trouble, we can call it quits and you’ll just be normal again. You should barely even notice it at first though. Think of it like birth practice!”

“I guess,” she says reluctantly, “I don’t know much about it at all. You really have babies in your—I mean my belly?”

Sweet Pony Jesus, what have her parents done to this filly. “Yup,” I tell her, taking her hoof and laying it on my own belly, well, lower belly. “That’s where my foal is. I’ve been growing her for weeks now, and Windjammer didn’t even know.”

“Only because you didn’t tell me!” Windjammer said resentfully.

“It was still pretty incredible when I told you while you were doing it, right?” I say teasingly his way, “You still totally came in her.”

Windjammer blushes and looks away, so I tell him, “C’mon, you need to give your mommies some attention. We both know how cuddly you feel after you cum.”

He comes over and we all cuddle together, and Teacup’s now thorougly invested in the whole activity, murmuring gleefully, “Hee hee, I’m a mommy.”

“Just like your mommy,” I reply happily, “She and your dad were probably older when they did this though.”

“Well, I… I don’t mind,” Teacup says uncertainly, “You were right, it… I mean it just feels normal so far.”

“Your estrus is gonna stop,” I point out, “Fillies who are secretly mommies don’t have it, since the only point of estrus is to make you get a foal in you.”

Teacup blushed, but said shyly, “Well then I’m glad I… did. Estrus sucks.”

Then God waved her magic horn and nothing bad happened.