Author's Note

Contains: shapeshifting, reverse full tour, blatant lies, anal orgasms. In other news, I started a Discord server for the people that like my stuff so if you want to join DM me or add me on Discord at Horndog#3496. I'll be streaming my writing sessions there if you want to see disasters like this in real time.

Smooth (full tour, lunar shenanigans)

"That just doesn’t sound right."

"Don’t you trust me, sister?"

Celestia looked down at the navy blue shark peering up at her from the edge of the tank.

"Honestly, Lulu, not really. You have to admit that your insistence that your current form is smooth in every direction yet your unwillingness to let me touch you to make sure before I let you swim up my ass is suspect."

The shark with the crescent moon cutie mark thought about this for a moment. "Alright, I can see why you’d have concerns. Are you really going to pass up an opportunity to have a shark wriggling around in that hungry posterior of yours, though?"

Celestia rolled her eyes to her heavens. "My ass isn’t ‘hungry’."

The shark grinned in the way only a shark could. "Verily? Thou dost not stuff it with every somewhat smooth object in sight? I have never caught you jamming fruits, tubers and other foodstuffs up it? I did not catch you just yesterday lowering yourself upon the finial at the base of the grand staircase's banister? Is your hungry hole not clenching upon itself at the very thought of having your younger sister wriggle deeply within as a completely smooth shark?"

Celestia’s expansive ponut did in fact wink hard at the thought of something wriggling deep within, and perhaps a shark would make an interesting change of pace from the tentacles she normally used when she was in the mood for something wriggly. "So I may have a certain preference for the pleasures of anal, but that does not mean I would be willing to let my sister swim up my ass, regardless of how smooth she claims to be."

"I could wriggle into your bladder instead if that is your wish."

Celestia shook her head. "No, that hole has always been more your thing. You’re far too large at any rate."

Making a lazy lap of the tank, Luna showed off just how flexible she was, undulating in all the right ways at just the right speeds. "Tis a shame this form doesn’t have a traditional urinary system." She frowned for only a moment before resuming her swimming. "I sure am incredibly smooth in every direction as I swim about this dreary tank though, wanting for some exciting space to occupy."

Celestia watched the lithe muscle ripple just beneath the smooth looking blue scales. A bead of sweat formed just above her ear, trickling down and causing it to flick. It had been some time since she had visited the seaponies, and while she had the opportunity to pet several sharks while she was down there, her memory was foggy regarding the exact texture of their skin. A needy clench of her nethers served to further cloud her judgment, several large drops of arousal dribbling down her leg. Her connection to the sun was a wonderful thing, but it left her in a state of perpetual heat, a heat that was normally quenched at least thrice daily. Watching her sister pirouette gracefully through the clear water, Celestia tried to think back to the last time she had gotten any release. Her morning session had been canceled due to a surprise visit from the youngest member of royalty, and her after lunch alone time had been postponed to its grave so that she could catch up with the meetings she’d shoved aside to spend some time with Twilight.

Her plot hole practically ached with emptiness now, an hour after she had set the sun. While she had the willpower to go weeks without relief, and had on several occasions, those times she had a good reason to do so. If things did go wrong, she supposed that she could just teleport her sister out. It wouldn’t matter much anyway. Alicorns were built differently from normal ponies, and she could say with confidence that she could do an awful lot to her rectum without damaging it.

"Completely smooth-"

"Oh alright, sister. I am unsure as to why you are so insistent that you must swim up my butt as a shark, but if you are this desperate, I see no reason to deny you this."

Luna’s sharky grin was even wider than before. "Tis not I, dear sister, who is desperate. It gladdens me that you are finally seeing reason though."

Celestia huffed, "Hush, you. Now hurry up. One of us doesn’t have all night." Spinning around, she hung her massive plot over the rippling water.

Seizing the opportunity before Celestia could change her mind, Luna swam to the bottom of the tank before darting upwards, exiting the water with a splash, her pointed snout striking true.

Celestia let out a shocked ‘EEP’ unbefitting a goddess as the cold flesh of her sister’s current form slipped into her hot depths with ease, half of the two foot long fish sliding past her experienced ring in one smooth motion. Almost instinctively, her hind legs went ramrod straight, her front legs giving out to thrust her ass in the air.

Luna used the change in orientation to her advantage, her attempts to wiggle deeper now assisted by gravity. Grimacing slightly as the powerful muscles of Celestia’s rectum clenched around her, she used the additional friction to pull herself even deeper.

Celestia was in bliss. The tentacles she normally used wriggled plenty, but they never really felt truly alive. The way her sister contorted and struggled against her own powerful muscles rubbed all the right places in her in just the right way. Before Luna even reached the back of her rectum, she experienced the first orgasm of the night.

With a mighty clench, the incredibly experienced muscular ring that was wrapped around Luna’s midsection nearly crushed her. Riding out the first wave, she used the subsequent clenches to work herself in to the base of her slender tail. As the earthquakes calmed to tremors, Celestia grunted.

"Alright, Lulu. Thank you for that wonderful orgasm, but you should probably come out now. I’d hate for you to suffocate."

Though her voice was deeply muffled, Luna’s reply was firm. "Tis of no concern; I cast a breathing spell in advance!"

Shuddering at the vibrations caused by somepony talking in the depths of her ass, Celestia frowned. "Well you need to come out anyway, even I don’t have enough room in there for you to turn around."

The tail sticking out from under her tail gave a wiggle. "What was that? I couldn’t quite hear you through your prodigious behind."

"I said you should back out! Even if you wish to continue to pleasure me, wiggling in place isn’t going to do it."

The wiggling stopped completely. "I cannot."

Glaring at her own butt as if the shark within could see, Celestia exclaimed, "What do you mean you can’t?"

"I can only go forward. Have you ever seen a shark swim backward?"

Lighting up her horn, Celestia grabbed hold of the tail that was tickling her dock (most pleasantly). "All right, here!" With a mighty tug, the shark didn’t budge an inch within her rectum, though a ring of pink was exposed for a moment within the wrinkles of her white ponut. Giving another couple of tugs, she confirmed that Luna was quite stuck.

"Luna." It wasn’t a question.

"Alright, so I may have fibbed, but only a half fib."

Sighing deeply, Celestia let go of her sister’s tail. "Let me guess, you’re only smooth in one direction."

"Not completely smooth. I’m sure you can feel the texture, though your rectum would seem to be gripping against me quite well in the other."

"Alright, let me teleport you out."

Luna shook her head, sending a muted wave of pleasure through the older sibling. "That won’t be necessary!"

"Are you going to teleport yourself out then?" Celestia tried to ignore the continued sensations from her rear end as Luna shook her head again. Her last orgasm had been nice and all, but even now she could feel the burning need growing again. "Well, what are you going to do then? You can’t turn around in there and you can’t back up."

"I’m going to do this!" With a mighty twist, Luna pulled her tail through Celestia’s tight ring. Taking advantage of her sister’s shock, she deftly wormed her way deeper, using the bend into Celestia's colon and the one-way nature of her skin to heave herself forward inch by inch.

Celestia cried out, her nethers winking powerfully and sending a splatter of her juices to the floor. Few things had ventured that deeply within her, though she had to admit that that was mostly due to her relative size. Finding things long enough to even make it to the back of her rectum was disappointingly rare. Pulled out of her delirious musings as Luna rounded the next bend into her transverse colon, she glanced down at her stomach, only to be disappointed that the only sign of the relatively large object within was a slight jiggling. Resolving to do something about her cake-fueled pudge later, probably, she groaned aloud as her sister continued her assault.

Luna was certain that were she not an Alicorn, she’d be worn out by now. Wiggling through the tight tube was a lot of work, and it was awfully hot in here, but she was rapidly learning the best way to make progress. Nosing up against another bend, she paused for a moment. Lighting up her internalized horn, she summoned a light attached to the tip of her snoot, though all that was revealed were the trembling pink walls of her sister’s gut.

From outside, though, Celestia noticed the soft glow shining through the walls of her abdomen, right beneath her rib cage. "Oh Faust that’s deep. Luna, how deep do you plan to go?"

Instead of answering, Luna simply pressed forward until she felt a much tighter passage at the end of her nose. Gauging the tremors of the walls around her, she wiggled in place for just long enough to send Celestia over the edge again.

Riding out a second mind-bending orgasm, Celestia only subconsciously noticed the peculiar sensation stretching from a spot she’d never stretched before.

Luna found her current tunnel to be even hotter and tighter than the last, though as more of her slipped in, the additional tightness only helped her progress faster. Focused as she was on venturing deeper, she was totally unprepared for a jarring impact, her surroundings shifting around her disorientingly.

Celestia, overwhelmed by the feeling of things entering a place she’d never used before, on top of a powerful orgasm even by her standards, collapsed on the floor, rolling onto her back. Panting, she tried to ignore the sensations from deep within herself, though it was a losing battle as the evidence of her arousal dribbled across her rapidly winking ponut and soaked into her tail. Lifting her head to look for the light, she watched enraptured as it inched back and forth across her stomach, every movement corresponding with an odd, though arousing feeling in her small intestine as her sister’s textured skin rubbed past her walls.

Even despite Luna’s Alicorn endurance, she was starting to wear out. Her brilliant plan to ensnare her perpetually horny sister to satisfy a fetish she’d gained from one of her subject’s more questionable dreams hadn’t accounted for just how long the digestive tract actually was, or how hard it would be to propel herself through it. From the vibrations of her sister’s moaning that she could vividly feel through the flesh around her, she must be getting close again. Maybe after that orgasm she could ask Celestia to teleport her out.

Just as Celestia's moans reached a crescendo, she felt the first true resistance of her trip against her snoot. Pressing forward, she was surprised as it held against her. Gathering herself, she rammed against it with the last of her strength, slowly opening what turned out to be a tight sphincter. With a sudden lurch, she shot forward.

Celestia shook in orgasm, a very weird, though incredibly intense one brought on by parts of her getting violated in ways they shouldn’t be. Holes clenching against nothing, sore legs shaking violently as exhaustion crept up on her, her mouth dropped open in a wordless cry as she felt a sudden fullness. Coming down from her orgasm, she tried to identify where the light within her was coming from. "Luna?"

Luna replied wearily, wrapped into a ball by the shape of her current confines. "Yes?"

"Where are you right now?"

"If I had to guess, I would guess your stomach."

Laying on her back, a thin sheen of sweat coating her body as a thick layer of fluids swamped her entire hind end, Celestia giggled breathlessly. "Wow."

"Yeah, now, if you don’t have any objections, could you teleport me out?"

The giggling stopped suddenly. "Uhh... about that."

"Tia."

"You see, normally I’d say yes to your every command, within reason, but after three mind-blowing orgasms in a row at the end of a long day, there’s no way I could concentrate well enough to teleport you out safely without harming one or both of us."

"If that is how you wish it to be, then." Gathering her strength, Luna nosed around until she found the hole she was looking for.

"Luna, what are you-" Celestia’s eyes went wide as she felt the unmistakable sensation of something traveling up her throat. Gagging around the obscene bulge that formed, her jaw was forced uncomfortably wide as Luna slithered across her tongue to flop onto the cold stone floor.

A bright flash later, and a wet and bedraggled blue Alicorn popped into being next to her, panting heavily.

Still gagging slightly at the fishy flavor, Celestia glared lightly at her sister. "You could have warned me that you were going to do that!"

Eyes still closed, Luna raised an eyebrow. "What did you expect me to do?"

"I don’t know, teleport yourself, turn to smoke, something!"

"Oh. I do suppose I could have turned to smoke and had you burp me out. Actually, no. That sounds unsavory even to me." Wrinkling her snoot, Luna made a face.

Forgetting her indignation for a moment, Celestia giggled. "I feel that you would have made a fine, strong belch."

"Blegh. Please do not speak of this any further, you really are what they would call ‘gross’, sister." The twitching corner of her mouth betrayed Luna's mirth, though she managed to hold on to her composure for a moment before they both descended into tired giggles.

Finally catching her breath, Celestia turned towards Luna, flopping onto her side. "Thank you, Luna."

"Oh?"

"For convincing me to try something new. I have to admit that over the past few centuries I’d fallen into a bit of a rut with my rutting, and besides the occasional fruit or banister, I’d stopped experimenting. My needs were simply that, needs. Something to satisfy as quickly as possible and then move on." Taking a moment to think, Celestia shook her head. "I don’t think this is something I’d like to do every time, but I should branch out more. Even as old as I am, I still haven’t tried a great many things, and if you’d like to join me for it, I’d love to have you with me every step of the way."

Luna opened her eyes to give Celestia a flat look. "How much of that last part was a preprepared speech?"

Celestia looked away sheepishly. "Most of it. I’ve been preparing for my retirement and wanted you to join me."

Luna simply rolled her eyes. "You just want me to find new ways to pleasure you, don’t you?"

"Well, yes."

"Why didn’t you start with that then? I’d love the opportunity to continue to claim the largest plot in the land!"