She seemed captivated by his erecting penis, so he blushed and stopped drawing to tell her, “S-sorry it’s just... it goes back in after a while.”

“Oh, you don’t know why your... penis is coming out all on its own?” his soft pink furred babysitter asked.

“Not really,” he admitted, “My dad just says I’m growing into such a big young stallion.”

The babysitter didn’t answer at first. She bit her lip. He was starting to get nervous again, when she said, “You want me to show you why it does that?”

“O-oh, I guess?” he said, not sure why the babysitter cared about how his private parts had been misbehaving.

She climbed off the couch, while he looked up at her from where he was drawing at the table. “Get up on the couch,” she said, a conflicted look in her soft green eyes, “I want to show you... something.”

He did, and the babysitter turned her back to him, looking his way and saying, “Your penis... is supposed to go into *my* special place. T-the special place of any female, really.”

“Your... penis?” he asked, unable to comprehend just how his penis would...

Lifting her tail, and shifting it subtly off to the side, she blushed and said, “No, silly. I don’t have a penis.”

“Y-you don’t?” he replied, looking under her tailhole, and seeing only a strangely alluring slit between her legs.

“Fillies don’t have them,” she insisted, “Take a look at my... vulva. That’s what I have instead of a...” She paused, hitching up a breath as her vulva flexed strangely, scrunching up and opening to a glistening pink, before stretching back out into that ordinary slit. He squirmed; his penis was really... big and stiff now. “A penis...” she sighed dreamily.

“M-mine is *really* I mean it’s supposed to um... b-be like this,” he shakily stated, “Your uh... vulva keep moving.”

“That means I’m in heat,” she said in a sultry voice, “When I’m in heat, that means if a colt cums inside me, I’ll get pregnant and... have his baby.”

“I don’t wanna be your baby,” he protested fearfully, “How would I even	*fit?”*

Blushing heavily, the babysitter stammered, “N-n-no not you, I mean just your penis.” She edged backwards towards him, as he felt a strange hunger rise in his deep belly when she winked for him again, “If you put your penis in there,” she said softly, “Then you’ll feel an urge to slide in and out of me. It’ll make you feel better and better, until you *climax.* Then you’re gonna p-push your penis in and it’ll start jerking. P-pumping. You won’t be able to stop. You’ll feel your... semen bursting out of it, going up deep inside me.

“Your semen...” she breathed, practically sitting on him on the couch she was so close. Her marehood had a dizzying spice to it, something that made it seem *very* appealing. “This white... goo that just comes outta your penis,” she continued, “If you put it inside me, it’ll... f-find my egg, and turn it into a foal. It’ll grow in my belly, bigger and bigger, u-until I have to give *b-birth.”*

And then she outright rubbed her slick labia along his shaft, smushing him into the couch with her ass as he tried to get his forehooves to grip it weakly. “You wanna be a daddy?” she asked in a low whine, “If you cum in me then I’ll push your baby out right...” Lifting off the dazed colt’s lap, she stepped forward enough to show him, spreading herself with a foreleg reaching back there. “Right *here,”* she said, “It’ll just squeeze outta me, a-and then you’ll be a daddy. Just like your daddy... put his semen inside your mother, to make you.”

Dropping her tail very slightly, she said, “S-so that’s why your... penis is getting hard. To get big and long, so it can go deep inside me, and leave your seed. My heat makes me want it.” Her voice grew tense, as she admitted, “My heat makes me wanna push a foal out there, and have a big belly, and have a penis inside me. I can’t... r-raise a foal or anything, so you shouldn’t. F-finish. Unless you wanna be a daddy.”

“I–I don’t know,” he said in confused concern, because he wanted to do that, but what did it mean for *him* to be a daddy?

“You might have to... take care of a little baby foal sometimes,” she said, guiltily, “A-and change his diaper, and... and take him to school and stuff. I’d try to help, but if you’re the daddy, you’d have to be like... like your daddy. He has to work, to um... help you grow big and strong. And you’d have to do... that.”

“That sounds terrible!” he replied, and it broke his heart that her ears went down at that. “I–I wanna, but... but *I’m* going to school. Am I gonna have to... go to work??”

In a frustrated blush, his babysitter said, “You don’t have to finish though.”

“Huh?” he asked.

“You can just put it in me a little bit,” she said, “If you feel like something’s happening, you can pull out. It’s only if you put it inside at the very end when you start cumming, only then does it put a foal in my belly. S-so just try it, okay?” Hiking her tail up again, she backed back to the couch. “And when you feel yourself... o-overflowing with pleasure, you can pull out. And I’ll... help you finish, then.”

He wanted to say no, but he *wanted* to say yes. She winked again under there, a trickle of her lubrication oozing down, and he said, “S-so just... how do I get it in there?”

“Mount me,” she stated in lusty relief, “Climb on my rear with your forelegs. Y-you’re on the couch, so you should be able to put your penis in, if you... hug my butt. J-just do what comes naturally.”

He tried climbing on her butt, and declared, his hooves barely reaching around her big thighs, “I-I think it is! My penis’s all... wow, you’re *wet.”*

“It’s so you can slide in and out of me,” she said curtly, “Just feel around, try to... get it deep. I need you to... to put it deep. There’s a place near the bottom, that nnf... you feel so hard, you little colt.”

“I...I do?” he said, wiggling to feel around in his babysitter’s glorious, warm sliminess.

“I can feel you with my marehood,” she purred, as he levered his penis with a forehoof, and it... sort of stuck in her. He *had* to push, soon as the head of his penis was enveloped in her flesh. “You can feel my... my vagina with your colthood.”

“I... I have to push!” he said, alarmed at the feelings rising up in him, powerful urges he’d never felt before. “This is... okay?” he asked, thrusting deep into his babysitter’s pussy.

“Ohhh yess,” she moaned in delight, “I feel your... penis. Just pushing *into* me. Y-you can feel how um... hot I am in there, right?”

“Y-yeah!” he said in shock, his forelegs hooked on her thighs, an urge to pull out rising up even stronger than the one to penetrate her.

“One... squirt from your penis now, and I’m pregnant,” she stated indulgently, pushing back against his hips, making him step back with his hind legs. “If you push it *deep* like that. You need to... p-pull out and push in again. Do it over and over again. Then pull all the way out... oh Celestia you’re *inside* me. Then pull...” he started thrusting because he *had* to, “All the way... out and... you won’t be a daddy.”

“Ohh, you feel so *good,”* he moaned, hugging her and humping into that beautifully hot, slimy passage, sliding all around his cock again and again.

“You... wanna be a daddy now,” she stated more than asked, as she panted in the urgency of coitus, “You’re gonna push it... deep, when you cum. Just keep... in and out and in and yesss. When you *cum* you’re gonna push it deep and...”

“I... I think it’s....” he said, desperate to do whatever this cumming thing was. He never wanted to leave her. In and out and in and out. It was rising in him so fast! Some tingling, powerful... something.

“Gonna have... big... round belly,” she murmured, “You’re gonna... you *want* me to have one. You’re gonna... cum with your *penis* and it’ll h-happen to me~!”

He didn’t reply, just moaned and humped harder. He wanted this thing to make her belly big, and she said she’d squeeze out a foal from right where his penis was. It rose in him like a tidal wave, just like she said, something desperately important flooding into the deep base of his penis. “I’m gonna do it!” he squealed, “I’ll push deep! You’ll... gonna make you... ohh it’s... it won’t stop it... ahh ahh AHH”

“Push deep! Push deep!” she cried out, when the first jet of cum in his life fired up into her vagina. He pushed as deep as he could, and he couldn’t stop his penis from jerking in her, from invading her. Moaning, he clung to her rear, panting as inside there, his penis was spurting burst after burst of cum up as deep into the birth canal of this mare’s ass as he could get it. Holding her and spurting within, he imagined it finding an egg in there, and just... growing inside her. He *needed* to do that to her. He felt like he was falling into her, when he came, hot rushes from his penis vanishing into the mysterious depths of his babysitter’s rear end.

The next time they met, they started doing it right away. Every time his babysitter came over because his parents had to work, he clung to her butt, letting his cum fill it up with foal. Over the year, his penis seemed to be bigger and thicker every day, turning from a little thing peeking out of his sheath, into a thick, dangling tool swinging between his legs. It took control of him just as much as it did her. She showed him her belly growing, and it just made him wanna do her even more. She lay on her back, so that he could hug her pregnant belly as he pushed up into it and came inside her again. 

She screamed when she gave birth, far from any prying eyes, snuck away with him, but she insisted it was the greatest thing ever. He tried to help, but he couldn’t even really fuck her with how *changed* her vulva had become. She just wanted him to see while she stood there and grunted and squealed, her belly flexing powerfully to push that foal out of her, in a way that she said she couldn’t stop doing.

Then her labia stretched open like a rubber band during one particularly intense push, and the head and ears of a pony emerged. “It’s coming out!” he called out in shock, “You really *do* have a pony inside you!”

“Your foal,” she moaned, “You can see your foal.... nnnnrrrgh!” and she belted out that frustrated cry as the foal’s head slipped right back in, leaving her labia slid closed again, only a slight blush indicating that they’d been stretching around a foal before.

“The head is...” she said at last, in palpable relief, “The head is out.”

“Yeah, just... hanging between your legs,” he said faintly.

A shaky laugh hit her at that. “Yeah I’m just... half birthed. Stars, there’s really a... foal hanging outta me?”

She lay down for the second part of the birth, a dissheveled picture of a birthing mare. She cooed at the infant between her legs, who woke up at some point, and looked between her and him in uncomprehending confusion. The foal’s forelegs were out, so he played with them a little, and they... sort of rested their forelegs on the curve of their mother’s belly.

Eventually, she said, “Oh, I think it’s... starting again. Yeah definitely... starting to feel an urge to push.” Smiling down at the now sleeping infant, she said, “Guess I’m gonna... finish giving birth to you now.” She breathed harder and harder then, telling him about how it was filling her up, like with sex, but a painful squeezing push at the end of it. He held her hoof at least, then stroked her belly, so she could feel it, saying, “Those are the... the *birthing* muscles I have to... to squeeze, more and more. I can’t stop, I... wanna... I wanna... oh here it g-goes,” One more shaky breath and then a squeal burst out of her, as beneath his forelegs, her belly clenched down powerfully.”

“Oh it’s... squeezing so... so hard!” she gasped, laying back and staring intensely at her own pregnant belly. She squealed again, and something shifted within her, as the foal started... squeezing out, more and more present between her legs. She even moaned about that after a contraction, just saying senselessly, “My *legs* I can feel her lying between my *legs...”*

She was a little embarassed at how much she lost it back then, once the foal had slipped out entirely. But it didn’t stop her from murmuring in satisfaction as the foal suckled at her teat, while she indulgently gave birth to the placenta. “It’s just sorta... *splurging* outta you,” he said faintly, as they watched what was emerging from her groin.

“Yeah it... yeah can’t... nfh stop pushing it... more... out,” she commented, “It’s bigger than I... thought it’d be. H-holy crap giving birth is gross.”

“At least you’re not pooping anymore,” he stated solemnly.