You drop Moonie onto your king-sized bed with a POMF, set your shopping bags down next to the bed, and collapse on top of your marefriend. You go for a kiss...and her hoof presses against your mouth.
>"Anon! You can't just emaresculate me like that! Especially in front of my former friends! They'll think that I'm weak and that you're a huge slut!"
>You're tempted to ignore Moonie's protests and bury your face between her legs, but you actually respect her as a partner. She's wonderful. She can have an intellectual discussion with you about social sciences, literature, and pottery. She doesn't condescend to you when she's discussing magic or hard sciences, which are both well outside your ballpark. You have enough hobbies in common that you can spend time together, but she likes a few things that you don't, and vice versa, so you get a little time apart, 
>Also, she's enough of a slob that she doesn't squawk if you get a day or two behind on the housecleaning.
>Most importantly, she actually listens (and usually agrees) if you ask her to stop doing something that bothers you, instead of having a solipsistic freakout like most human women would.
>You pull her hoof down and rest your head next to hers, matching your inhalations to her exhalations.
"I'm sorry, hon. I got carried away. You do that to me." 
>You nuzzle into her chest tuft. 
"I was originally planning for that to be a private show, but since your friends showed up, I figured being all over you would make you look good. After all, I didn't see any of them bringing their lovers along. Unless Purple Nurple there is dating the mini-dragon."
>"Eww! No, Spike's like Twilight's little brother!"
"And I'm supposed to know that how, exactly?"
>"Ugh, you're right. You couldn't be expected to know that. You've never met them."
"Mm-hmm. Still, it is good of them to come back and ask you to forgive them. Are you going to?"
>"I don't know. It really hurt when Twilight completely abandoned me. I could have forgiven her for skipping my party, given that she ran off to save the world, but what really hurt is that she completely ignored me afterwards. She didn't even apologize, she didn't write, she didn't visit..."
"That's true, but she's here now. Better late than never isn't always true, but she's at least trying, and neither of us are the pinnacle of social skills ourselves. I'll follow your lead, but I think you should at least give her a chance. But be honest with her about how much she hurt you. Trying to sweep it under the rug won't help you achieve catharsis."
>"Nnnnggghh." Moonie sighs. "All right. I'll try. Next question: WHY are you dressed like something out of a pulp fiction cover, or a Playmare centerfold?!"
"I thought I explained that already. You've stolen my heart, Moonie-Moons. I love you. I can't help but love you. I wanted to show you."
>"Why? I'm nothing. I'm nopony. I'm a miserable nerd and I don't matter -- AAAAHHHNNN!"
>You pry your face out from between Moondancer's thighs with some difficulty. 
"You matter to me. I think you're wonderful. I want to marry you, Moonie. I want to knock you up and have a bunch of little mutant children."
>"MARRY ME?! I -- I -- HNNNGGGHHH."
>You bury your face back into that wonderful cheesecake-flavored horse pussy and get to licking, while your hands alternate between squeezing Moondancer's fat teats, playing with her fat pink horse-nipples, and stroking her G-spot. All the while, your tongue's busy massaging her winking clit.
>"AHHHHNNN!" A flood of cheesecake-flavored squash soup gushes into your mouth, and you gulp it all down. 
>Moonie breathes heavily as you break away and rest your head on her tummy. She rubs your head with one hoof, too worn-out to speak for the moment.
"Yup. Marriage. Wedded bliss. Babies, babies, babies."
>Moonie's still panting. You pull yourself up, rest your head on her chest tuft, and reach up to stroke her mane. After a while, your little mare recovers enough to speak. 
>"I thought you hated foals."
"Only if they're not mine."
>"How -- how am I even supposed to have foals with you? Not that I don't WANT to, but...you're an ape."
"Zebra alchemy, apparently. I asked Sunbutt the Cake-Rumped -- "
>"PRINCESS CELESTIA."
"--Princess Celestia for a boon in exchange for killing Tirek, and she delivered. Although she did lecture me about eating enemies of the state."
>"I won't lie, it's really disturbing, even for me. Any mare without a predator fetish probably would have run screaming at that point.""
"Well, I'm a lucky predator then. Omnivore, really."
>"'Hopeless soupslut' is more like it."
>You chuckle.
"Guilty, but I'm YOUR soupslut, Moonie. On a completely unrelated note, if I'm proposing, I have something for you."
>You dig into one of your shopping bags and pull out a golden horn ring set with amethysts, a matching finger ring, and a thick, murky white potion.
"Well, Moonie? Will you marry me? I know I'm not perfect, and neither are you, but we're both aware of that. Even if we argue sometimes, it's never over anything major, and we've been together for a year and a half. I think we've hit a lot of the usual rough parts. I can't imagine anyone, or anypony, who makes me happy like you do. "
>"Yes! Yes, of course! Yes -- MMMMMFFFF."
>Moonie cuts off as you do your damnedest to shove your tongue down her throat.
>When the kiss finally breaks, you slide the horn ring down over Moonie's horn, slide the other ring onto your finger, and pass her the potion.
"You first, according to the instructions. Take about half."
>She chugs her share, and then scrunches like she just ate a lemon.
>You down the remaining half, and then feel your own face scrunching up. It tastes like cheesecake, salty milk, copper, and bleach!
"Ugh. I'm glad drinking that stuff will only happen a few times."
>"Oh, thank Faust, I thought it was just me. Wait...what do you mean 'a few times?'"
"You didn't think I wanted to stop at only one child, right?"
>"I...I don't want only one foal, but I'm not going to be a foal factory either! I have dreams and goals and aspirations!"
"So do I. Don't worry, the rational part of me doesn't want a dozen kids. That's not good parenting. I was thinking somewhere between three and five."
>"Okay, that sounds reasonable."
"Good."
>You kiss her, then pull a bottle of your "special fun times pill cocktail" out of the nightstand. Moonie puts a hoof on your wrist before you can take it.
>"Honey, you made sure that those wouldn't have any sort of unhealthy interactions with the potion, right?"
"Yes, I did, but thank you for thinking about that."
>You kiss her. Then you chug the pill cocktail, and wash it down with a drink from the water jug on the nightstand. 
>Then you kiss your mare again. Then you start mixing the kisses with little nibbles, steadily moving lower...

>You must have swallowed a half-gallon of squash soup by the time Moonie begs you to "just fuck me already!"
>You grab Moonie's squishy thighs, pull her hips down to yours, and pin her hindlegs as close to her ears as you can without hurting her.
>With a single savage thrust, you hilt all eight inches of your monstrous monkey meat deep in the warm, welcoming waifu pussy.
>The raw, savage, searingly passionate mating press goes on from there.
>Moonie's cervix gives way towards the end, and she promptly clenches hard enough that for a second, you think your soul's left your body as you nut.
>Rope after rope after steaming rope of white ape-seed, twelve in all, floods Moondancer's womb.
>You think that probably did it, but you want to be sure.
>Very, very sure.

>Round two is doggy style -- or as the locals call it, pony style.
>Moonie wails and squirts like a fire hydrant when you bite her ear, neck, and shoulder while you plow her into the bed.

>Round three is slower, less crazed, but still intimate. You work through several positions.

>Be Twilight Sparkle, purple unicorn.
>You came back two hours later, because you figured Anon was giving you a load of horseapples when he told you to come back in four or five hours. 
>You were wrong.
>You can hear Moondancer's cries of passion from outside the house.
>Then you can hear Anon, too.
>"I love you, Moonie! I love you, I love you, I love you, I -- UNNNGH!"
>Faust, that hurts. It reminds you that you have an empty bed waiting for you at home.
>You'll come back later.

>Be Anon. You finally remembered the ribeye steak you'd brought home. With some difficulty, you tore yourself from Moonie's loving embrace, staggered into the kitchen, and chucked your steak into the icebox.
>Moonie followed you out, led you to the couch, and you spent most of an hour orally worshipping her before you were ready for round four.

>Round four is the last for today...and probably a day or two after this. Even with your pill cocktail, even with Equestria's healthy environment, and even being in the best shape of your life, you're not as young as you used to be.
>It's a slow, loving mating press that lasts a solid forty minutes before you finish.
>You pass out laying on top of Moonie, her hooves wrapped around your shoulders and hips.

>You both wake up to the sound of knocking.
>Moonie uses her magic to open the door, and her former friends make their way in, blushing heavily.
>Twilight and Twinkleshine wrinkle their noses, Lemon Hearts looks nonplussed, and Minuette...
>"EEEEE, ohmigosh! He put a horn-ring on you!"
>You decide that you like Minuette.

(There was going to be a bit here where Moondancer's friends question Anon about his intentions towards Moonie while she and Twilight are having it out, and then Twilight questions Anon about his intentions, but I can't be arsed to write it all out, except for the bit below.

>"Why DO you love Moondancer so much, Anonymous?"
"Well, she's wonderful. She can have an intellectual discussion with me about social sciences, literature, and pottery. She doesn't condescend to me when she's discussing magic or hard sciences, which I don't know nearly as much about as I'd like. We have enough hobbies in common that we can spend time together, but she likes a few things that I don't, and vice versa, so we get a little time apart, too."
>You nuzzle your face into her chest tuft, but your dick is too spent to do more than twitch.
"Also, she makes me feel safe. I can deal with physical threats, but I'm an alien here. I'm trying to learn about cultural and legal stuff, but there's so much to learn. I can trust her to protect me and not take advantage of me."
>Twilight blinks. "Okay, I wasn't expecting that."
"What, did you think I'm just an ugly face and a big dick?"

***

>Seventeen years later...

>You came home to find your satyr daughter and your reverse-satyr son (mostly pony from the waist up, mostly human from the waist down -- though he does have hands and a tail) spitroasting Twilight on the couch.
>Anonette's reclining on the couch, eyes closed, hands buried in Twilight's mane as the purple unicorn eats her out. Starchaser's plowing Twiggles from behind.
>Fortunately for your sanity, the couch faces the door, Starchaser's tail is long enough to hide his goods, and Twilight's blocking your view of Anonette's crotch. 
>Though you could have done without seeing your daughter's tits.
"Twiggles, when I asked you to help the twins with their homework, I meant actual homework, not  'anatomy homework.'
>Anonette yelps in horror. Twilight tries to neigh in shock, but Anonette's currently panic-squeezing Twiggles' head between her thighs, so the noise comes out as a "MMMMFFF!"
>Starchaser gives a horrified whinny, then groans. 
>You could have done without knowing what your eldest son sounds like when he cums.
>Twilight makes a noise that sounds like a horrified bleat, but it's still pretty muffled. (Anonette inherited Moondancer's tendency towards thick thighs.)
>You hear a crash. Moonie was a little ways behind you, bringing in a load of books in her magic. You're pretty sure she just dropped them.
>You turn around.
>Yup. Books everywhere. Moonie seems to be having trouble deciding whether to be horrified or furious.
>You are rather grateful that Anon Jr (human boy) and Sundreamer (filly) are still at school.
"I'm going to give you three --"
>You jerk your thumb back at the mini-orgy behind you.
"-- a few minutes of privacy to get some clothes on and sort yourselves out. Moonie, come outside with me. We'll deal with this once everyone has some clothes on again."

***

"And that's the story of how you were conceived!"
>Your purple centaur grandson, Evening Gleam (Twilight is not good at naming kids), claps his hands over his eyes.
>"Why, Granddad, why?!"
"Because it's fun."