It’s bath time in the castle, and as aide to the alicorn sisters you are required to join them in the tub.
There are quite a lot of things you’re “required” to do around here, some more dignifying than others. One day they’ll have you making a banana split with extra crushed nuts and the next you’ll be polishing their hooves or airing their bedsheets from the castle balcony after a night of vicious dutch ovens. 

Bathing the sisters is on the more tolerable side of things.
There’s one major problem though: the tub is only built for one alicorn, NOT two. And certainly not two alicorns plus a human. 

While the bath is drawing, you fetch some lavender and oat bath salts and shampoo from the bathroom cabinet. There’s a lot of stuff in here, but you’re quite certain the two sisters have only ever used about half of it.

You sprinkle some salts into the bath and the room soon fills with pleasant-smelling steam. Something tells you it won’t stay like this for long.

You pass by the window and press it open to the chill darkness outside. If you know the princesses as well as you think you do, this open window is going to be somewhat of a mercy. 

Celestia and Luna strut in, looking all regal and sophisticated.

They both squeeze into the tub first, leaving a tiny space between their gracious posteriors for you to wiggle into. No matter how you sit, you’ve got an elbow buried in royal asscheek or a shoulder brushing up against a warm crack.

Luna and Celestia sink below the surface with a tranquil sigh. They look like a pair of grazing hippos.
It’s a very tight fit, but the claustrophobia will soon prove to be the least of your concerns.

For whatever reason, these two never got the memo about bathing just after eating. Less than half an hour before their soak Celestia inhaled a twelve-storey cheesecake and half a bottle of champagne while her sister knocked back an entire pot of stew. The princesses are full of food, you can hear their stomachs getting to work on it.

And this ominous roiling of their guts has you sweating bullets, because it can only mean one thing.

The warmth of the water has a very immediate effect on the Princess. Easing their muscles, relaxing their stomachs. It’ll only a matter of time until your worst fears are realized.

“This is just the thing I need after the day I’ve had…” Celestia sighs.

“You can say that again…”

For a while all seems to be calm, except for the occasional stomach groan. You’re starting to think that they might be keeping their manners about them for once, sparing your senses by being polite and withholding their-

BRRRLLLP~!

The water buckles to your left. Bubbles groan out from the shadowy valley of Celestia’s crack and gather on the surface, popping like little fragrant bombs.

“Ahh… Such a relief.”

You and Luna both cast Celestia a sideways glance as the air grows rife with expired cauliflower and hues of curdled dairy and fermented grapes. Along with that is a light but palpable hint of vanilla. You can literally taste her cheesecake, though nowhere near as fresh as when she ate it.

“Manners, Tia.” Luna raises her brows and maneuvers around the tub. You watch her half-submerged plot swing to face you, and by the time you’ve clocked on to how close she has it hell breaks loose in the form of her own foamy storm. 

Those gurgling bubbles burst right in your face, singing your nosehairs with what’s left of the rich potato stew Luna ate for dinner. A vile savory reek to compliment her sister’s dessert-fueled aroma.

“Mmh… there, that one was far more polite!” 

Both Princesses giggle above you. You’re finding the whole situation less than amusing. 

However, Luna’s release was about twice as long as Celestia’s, and the sun Princess is not going to stand for such a thing.

She grunts, very gracefully, and all of a sudden the entire tub quakes with a low waterlogged explosion. You grip the sides of the bath for support as everything shudders around you. A violent jacuzzi shoots up from beneath Celly’s tail and erupt on the surface, sending ripples all the way over to Luna’s side. 

Five seconds pass before it dies down into a gentle stream of tiny shining orbs. 

“Mmn… beat that, sister~”

“I think I shall!”

Luna is quick to the draw. Short, but heavy, her retaliation disturbs the water for only three seconds but does so with enough force to push you back into Celestia. And the stench… it’s like rotten onions mingled with old soup. you’d plug your nose if only both arms weren’t trapped by your sides by the weight of the alicorns.

A chain of stinkers detonate either side of you like underwater mines, tickling your arms as they float up to the surface, then pulverizing your nose with a one-two punch of sisterly funk.

“Well?” Celestia speaks to you directly, “Are you going to clean us, or not?” She wiggles her fat ass, shaking you shoulder. The water sloshes about. Some of it splashes over onto the bathroom tiles.

Of course. How could you forget that they actually expect you to do the cleaning? 

“Right away…” you look around for the soap, and can’t find it at first.

“Looking for this?” Luna levitates it up at her end of the tub. You carefully pull yourself up to your feet and stretch your body over the top of her left buttock and her back, extending your arm. The soap’s just out of reach, of course, and Luna takes the opportunity to hit you with a point-blank ripper before dropping the bar into your hand.

Dizzy from her fumes, you twirl around and get to cleaning Celestia’s backside first, which she raises out of the water.

You scrub circles around her hefty plot, kneading it like dough, working up a thick lather. 
Of course, the moment you do this Celly shuts an eye and-
BLLLRPT
-breaks a hole in the wall of foam, covering your face in a warm spattering of bubbles along with a fresh coating of Celestial stink. 

You use an arm to shield your face from the onslaught of rotten, milky veggie gas and soap up her cheeks all the way to her cutie marks. Each one of these pillows is wider than you are—it’s really quite intimidating.

The entire time you’re lathering and rinsing her off with water she’s releasing a rapid-fire succession of steamy poots, mock apologizing after every one. You lean back to escape the smell, but Luna’s plushy plot is there to ensure you can’t get too much distance.

“Ah, I think you missed a spot, dearest…” Tia tilts her rump upwards, her cheeks parting. Her pucker pokes out, winks at you a few times and then blows your hair back with a powerful gust.
“No, my mistake! I feel quite lovely and clean back there.” She lowers back into the water.

“Now do me, wash-boy!” Luna commands. You go to turn around but the alicorns push their weight backwards into you in a coordinated attack.

As soon as they’ve got you packed betwixt their divine derrieres they loosen all manner of bubbly staccato pops and juicy horn blasts onto your writhing body. 

After much wrestling with their meaty plots you narrowly squeeze to face the sister of the night. She spreads herself with a hoof, revealing to you the shiny black blowhole that so dearly needs attending.

Unlike her sister, though, she doesn’t lift her rear for you to clean. It’s half-submerged, the water lapping at it. It feels nicer this way.

Taking the soap, you start to work around her flankhole, noticing the water grows ever so slightly dirty as you do so. Luna purrs and coos, finding your tenderness quite soothing.

“Celestia?”

“Yeeees?”

“Would you like to hear the new symphony I’ve been working on? I’m thinking it shall be my new anthem.”

“Symphony? Why, I didn’t know you played an instrument, sister!”

“Ah, but I do…”
You can hear something violent brewing within her. Oh boy.

PRRPPRRPLLT!! 
Her rabid fart cracks against the water’s skin, rippling it like the propellers of a motorboat.

“The lunar trumpet!” 

The two goddesses snicker, but all you can do is groan as you’re made to endure another raunchy stink bomb from moonbutt.

Now, it’s expected that the bowels of a literal deity would be able to cook up something potent, but even with those expectations you’re caught off guard by Luna’s stink every time.

Celestia’s emissions are loud. She’s a show off about it, but for all the power in her gusts she can never quite match her younger sister when it comes to sheer pungent intensity. All those years fermenting her guts on the moon paid off, it seems.

You move from her rectum to farther afield, massaging her buns. While you’re frothing her up Luna begins spewing out another deathly attack. This one’s softer and lengthier and the sound of It changes every time the water washes up over her venting hole. It goes from a crisp buzz to a bubble, alternating between these two tones all while the thick stink of it wafts up and into your face. After only a few more whiffs you decide you’ve lost your appetite for stew forever. All you’ll ever be able to associate it with is Princess Luna’s wind.

Soon (but not soon enough) she’s sufficiently clean too. Your work appears to be done, but the two leaders aren’t quite through with their fun.

“Acceptable job, huma-RuUuUuurp!”
Luna clasps a hoof to her face. That belch seemed to sneak up on her and it surprises Celestia just as much.

“Where did that come from?” She chuckles.

Luna smacks her lips. “If the taste is anything to go by, the garlic, methinks!” 

They share a giggle. You’re just glad this is a gassy release you don’t have to smell.

“You know, I think that glass of champagne might have a thing or two to say, it’s always talking back.” 
A look of supreme focus washes over Celestia’s face. She narrows her eyes, bloats her cheeks, and manages to force up an absolutely dynamite burp that disturbs the water surface and rattles all the bottles in the cabinet. 

HUUUUUUUOOORRRP!!!
“Ahh! Bloorp- excuse me!” 

Luna gives her sister a round of applause before letting out a deep, raspy belch into her hoof and wafting it around her face.

Tia smirks and lowers her snout into the water. You can hear the gas shooting up her esophagus before a barrage of bubbles spill out of her mouth and pop around her face.

At last, it seems that it might be over.

Celestia grunts and pours some more gusty bubbles into the tub, followed by a BLLORP from Luna, and with those parting remarks they both thank you quite professionally and get out of the tub.

The water level lowers to about half of what it was. You turn and lie down, drifting in the warm soapy water as you hear them grab towels and strut out of the bathroom.
Your arms ache, your legs ache, but more than anything your lungs ache.
As you rest there, staring up at the steam curling and swirling against the overhead light, all you can think about is how much the entire room reeks of methane.

The door creaks. It’s Celestia, peeking her head back inside.
“Don’t get too comfortable in there, little one. Luna may have her night shift ahead of her but I need someone to come and tuck me into bed. I might need you to stick around, too, for I fear there are thunderstorms a-brewing…” with these very ominous words and a girlish giggle, she disappears and leaves you to try and gather the willpower to go join her.