Tinker smiled as he waved to one of the royal guards, his tail flicking back and forth as he trotted out of Canterlot Castle. Finally, he had escaped from the princesses... Polaris had warned him about what it meant when one or both of them gained a fascination for some odd type of pony hybrid, but he had ignored the warnings.

Now he just had to figure out where they put his car... he trotted over to the door that led into the nearest royal guardsroom, and the door shut behind him as he headed inside.

And then it locked. Tinker spun around, his eyes widening, only to see the door on the other end slam shut behind Celestia. The mare wore a smirk as she walked into the room, and as her horn glimmered with magic, the strong scent of heat hit Tinker's nose, making him blush.

Without a word, Celestia's horn shot a beam of magic towards him, and he yelped as the magic hit him and coursed through his body, culminating in a heated warmth that began to gather in his nethers, forcing his cock to spill from its sheath and rapidly harden beneath him as he let out a weak moan.

Celestia closed the distance between them, grabbing onto Tinker with her magic and pinning him to the wall. Her magic wrapped around his cock, and she began to stroke it as she quietly hissed "You gave Luna an egg but not me!?"

His eyes went wide as he realized what was going on, and Tinker squirmed in a panic as he said "H-Hey! I-I didn't know dragon greed would do that!"

"Too bad, the moment I found out, I put myself right back into heat, and you now have the curse of Estrus, my dear Tinker~" Celestia growled, followed by a miscehiveous giggle.

Blushing hotly, Tinker asked "W-What's..."

"You're going to get more and more aroused until you successfully breed a mare, and I'm the only fertile mare in the castle right now, Tinker..." Celestia hummed, slowly running a hoof down Tinker's side as she squeezed his cock tightly with her magic. "Which means I need you to fix my heat again..." she whined quietly, putting on a pout that Tinker knew was fake, and yet it still made him blush.

Tinker shivered as he then looked down, to where Celestia cupped his balls with a hoof. He felt them twitch, then grow in size! As he watched, his balls grew in size by about an inch, making his eyes widen as he said "H-Hey! Is that the curse too?"

"It might be, my special little tweak..." Celestia growled. "So, which will it be?" She said, her magic releasing the stallion and letting him fall back to his hooves. "Are you going to breed your princess, or do I have to tie you up until you're begging to feel my pussy wrapped around your-"

Unable to wait any longer, Tinker grabbed onto Celestia, and he yanked her forwards, using the momentum from the white mare tumbling into his arms to spin her over, and lay her down on the floor. She let out a cute squeak as she fell to the floor on her back, and her wings splayed open as Tinker pounced on her, putting the white mare into a mating press as the tip of his cock squished against her heated, puffy, sopping wet marehood.

Dropping his voice to a whisper, Tinker hissed "Y-You guys are the hottest fucking mares I've ever met in my entire life, and I'm not getting off of you until you're pregnant, just like Luna is~".

Celestia arched her back, letting out a desperate whine of pleasure, and she cried out a restrained "Yeeesssss!" as her pussy began to squeeze tightly against Tinker's cock, unable to get a grip on his flare. He blushed hotly as he realized the mare was cumming, and Tinker growled as he thrusted forwards, plunging his cock into the mare's orgasming pussy. Her walls immediately clamped down around his cock, milking his length and making it hard for him to move as he stuffed his knot inside of her. With how badly aroused the mare was, Tinker was able to get his knot into her without needing to pop his flare into her womb, which was just fine for him.

Tinker flinched as he heard a sudden knocking on one of the locked guardsroom doors, followed by a gruff voice barking "Who's in here!? Unlock the damn door!" Celestia sucked in a breath, and Tinker grabbed onto her snout with a paw, clamping her maw shut to muffle her moans.

Whether the stallion got in or not, Tinker was fucked in a few different ways, so he turned his back on the door, even as it began to rattle. Bracing himself to hold back his moans, Tinker held onto Tia's maw as he pulled his knot out of her, starting to thrust into her as fast as he could.

The room was filled with nothing but the quiet sounds of Tinker's growing nuts slapping against Celestia's flanks, and the wet, schlk-schlk-schlk of his cock plunging into the white mare over and over, only stopping when his knot mashed against her clit before he pulled back again.

Within a minute, both ponies were right at the edge of orgasm. Celestia was quivering and squeezing Tinker's cock tightly, and Tinker was flaring, the tip of his cock massaging Celestia's walls firmly as he dragged it back and forth inside of her. And yet... neither of them came. Tinker found himself bucking faster into Celestia, changing the angle of his thrusts, but even though his cock was repeatedly firing gushes of precum inside of her, he wasn't able to cum.

He had a suspicion, that it had something to do with the curse she'd given him, but he didn't know what, and he didn't trust her not to make noise if he pulled his paw away. However, he also needed to. Celestia was struggling to handle the pleasure of being right at the edge of climax, and she was almost squirming enough to throw Tinker off!

He pulled his paw away from her maw, grabbing onto her for stability, but then Celestia let out a shaky "Yes! H-Harder! T-Trust meeee~!" Moments after, Tinker heard the hard rapping on the door again, and terror gripped his spine, sending a shockwave of panic and arousal through him as he lunged, locked lips with Celestia, and muffled her with a kiss.

His magic faintly glowed in the back of his throat as he plunged his tongue into Tia's maw, slithering his tongue down her throat to muffle her loud moans. And if he were honest, it helped him keep quiet as well.

Tinker's balls were even bigger now, and they began to slide along the floor with each of his hard thrusts into Celestia. Tinker was growing even more impatient and pent up, so he doubled the power of his thrusts, starting to ram his knot into the princess with every hard thrust.

She cried out into the kiss and thrashed beneath him, but Tinker held on tightly as he plowed the pony princess, ruthlessly knotfucking her against the floor as his balls churned with pent up cum.

As Tinker was pulling out of Celestia, his balls twitched, then they bulged in size one last time, his sack swelling even further as his nuts hit the landmark of holding an entire gallon of cum. Each. Suddenly, Tinker felt his hips spasm as magic gripped his body, and he cried out into the kiss as he was roughly thrusted back inside of Celestia, his knot popping inside of her one last time. Tinker's flare almost squeezed into Celestia's womb, but instead, her heat-ridden chamber was powerwashed with a strong jet of his cum, making her scream into the kiss as the spell finally let- and in fact forced- both ponies to enter a shared climax together.

The magic bound their hips together as Celestia's pussy began to milk Tinker's cock, working with his body to drain his balls into her womb. Both of them shuddered and moaned against each other, so eager to breed that they were left unaware that the magic was keeping their hips bound together by force. The curse that Celestia had placed on herself and Tinker was designed for forcing two ponies to breed, but in this particular case, she used it to ensure that she would get her own egg out of Tinker before he left to go back to Ponyville.

For minutes, more than long enough for both of them to lose track of time, the two ponies embraced, moaning and holding each other tightly as their orgasms gradually ran their course. When Tinker's balls ran dry, the curse was finally broken, and both ponies weakly sagged as they were freed from their orgasms. They didn't end right away- Celestia's gave out first, leaving her helpless to do anything but shiver with arousal as Tinker continued to pump a few more splurts of cum into her, but then he finally ran out.

The dragonpony sagged onto her wearily as the orgasm sapped the last of his energy, and he slowly began to retract his tongue from Tia's maw as she ran her hooves through his mane. Once he regained the strength to pull back from the kiss, he couldn't help but smile and blush as he looked down at Celestia, quietly saying "Y-You and Luna are the hottest mares I've ever met..."

Celestia smiled, kissing his nose, then she teasingly said "And you're my favorite pony halfbreed~" as she lovingly squeezed his cock, giggling softly as she forced a cute moan out of him. A faint shimmer of magic broke the silence, and both ponies looked down to see Tinker's cutie mark shimmering into view on Celestia's belly. The two ponies looked back at each other again, one blushing, one excited, and they closed the gap between them one more time, lips meeting for a final sensual kiss before they had to seperate.

✩｡:*•.──────────.•*:｡✩

Celestia fluttered her wings, then she unlocked both doors to the guardsroom. Swinging open the one that led outside, she trotted out with Tinker in tow, smiling as she nodded towards his car, parked and waiting at the bottom of the steps outside the castle. Her gut was still heavy and warm with seed, but her magic kept it effortlessly concealed.

"And there you are, Tinker..." She quiety hummed, as if he hadn't just bred a foal into her via a rushed session of frantic lovemaking. At the top of the steps, Celestia leaned down to nuzzle him, and she levitated two matching metal boxes in front of his snout for a moment, before dropping them into his saddlebags. "A little something for when you miss us..." she quietly whispered, "I only trust my favorite ponies with these, and they'll only work if worn by you".

"W-Well thank you, Tia..." Tinker said quietly, still wearing his blush from before. She giggled, then she planted him an innocent kiss on the cheek- ponies could see, after all, so it was only polite kisses for now.

"Make sure to have them next time, perhaps we'll take advantage of what they do... just make sure you're alone when you try them, okay?" she hummed.

"O-Of course!" Tinker said. "S-See you next time..." he shyly said, as one of the castle maids came trotting out of the castle. Celestia turned to greet her, and Tinker set on his way down the castle steps.

✩｡:*•.──────────.•*:｡✩

Luna gasped, staring into the mirror at herself. She slid back on her bed a little bit, looking down at her teats... they were the same as always, blue and plush and soft... with her marehood below, and her ponut below that. Everything was in place, the blue glow of her magic, her eyes, her flowing mane, her cutie mark, all of it.

She reached for her neck, grabbing a small metal charm, and she slid the necklace that held it over her head. In the span of moments, Luna dissolved away, revealing Tinker. He gazed at the charm in awe, before returning it to its sturdy metal box.

Picking up the second necklace, Tinker slid it over his head, and he shivered as the magic took hold, transforming him before his eyes. He- She became taller, her fur painted white, her mane starting to flow as it split into ribbons of color. Celestia's voice spoke back to herself as she said "That's incredible... even my magic..." in a soft voice.

And just like before, she couldn't resist looking between her- or Celestia's- hind legs, and at the soft, pillowy teats between them. Now she understood what Celestia meant when she gave her the two boxes. Tinker could have either of the princess, anytime he wanted... only problem was, he would become them.

As she slowly ran her white, delicate hoof through her soft chest fur, Celestia admired her body in the mirror, watching as her cheeks bloomed a warm red. It was a new experience, taking the form of a princess, but... Tinker liked it. Tinker really liked it.

Author's Note

ok fine I couldn't help myself both princesses get an egg

dunno what they'll do with it but I guess it's up to them whether they wanna hatch em or not

and thus finally completes the original saga of me putting my sona through things i have absolutely zero real experience with

though I doubt anyone would wanna read "Tinker and the mystery of why this ceramic tree limb has a crack in it"

hehe, love you guys, if you've read this far I hope you're having a great 4:50 AM!