You are an emissary from the Human World, invited to attend the Grand Galloping Gala.
You arrive through the portal and are greeted by a Royal Guard who escorts you to the Reception Hall where you take your place among the other dignitaries from foreign lands.
Once the Two Sisters have greeted the heads of each noble house in attendance they dismiss themselves and everyone else, except Princess Twilight, who must remain and greet the remaining guests as they arrive.
You wade in amongst the pastries, nibbling casually on this and that until you bump into the the sun sister. She is pleasantly surprised to see you, praising your evident interest in sugary delicatessen.
You take note of her expertise in this area, evidenced by the princess’s doughy frame and the way she carefully weighs her choices before selecting a specific item from the vast selection. Her manners are impeccable and she savors every bite with intense focus, her eyelids fluttering and her eyes rolling back when something she really enjoys touches her tongue.
Her flowing mane and tail are every bit as colorful as the confections, and once in a while her tail surges in reply to an intense flavor, giving you a glimpse of her corpulent thighs and weighty buttocks. Buried beneath and between the chalky flesh of her hindquarters you might be able to see her well-hidden anus and pussy if you could just get your hands on those flanks.
Even with all the cake and cream around, you hunger for those particular delicacies the most.
The aristocrats give her a wide berth out of respect, or perhaps cowardice. The princess is an intimidating figure, majestic and powerful. She towers over the ordinary ponies, and you have no doubt that she could flatten your delicate human frame even through you are uniquely tall enough to look her in the eye.
In spite of your misgivings you make fast friends with the princess, and soon enough you find you are enjoying each other as much as you are enjoying the fare.
“Try this one.” she says to you, lifting a sliver of vanilla cake with her magic and fitting it between your parted lips. “Good, don’t you think?” she says, her eyes half-lidded, a corner of her mouth upturned.
You nod your head, swallowing as your mouth fills with saliva before you select something you think would be appropriate for her.
“Here, close your eyes.” you instruct and the princess playfully obeys, blushing as she holds open her jaw and uses her magic to brush her mane behind her ear. You place a creampuff gently on her tongue, and when she closes the pastry bursts in her mouth, spurting cream into her cheeks and down her throat. She swallows it, her surprised expression melting into a mix of bashfulness and satisfaction.
“Good?” you ask. She nods her head.
Convinced, you reach out and fetch one of your own, but drop it into your cleavage when somepony bumps into you. They look annoyed, until they notice the company you are keeping, after which they apologize and slink away.
Before you can retrieve the creampuff the princess bids you wait, leans in close and puts her face in your bust to snatch it up, her tongue teasing the tops of your breasts.
She looks you in the eyes as she swallows, your heart beating hard in your chest, then opens her mouth is if to prove it.
You find yourself blushing, and a sudden gust stirs your dress and causes you to draw closer to the princess. When she does not object you go a little further, placing your hand upon her flank.
She feigns interest in something, playing unaware as your slide your palm around to her buttocks, feeling the various folds of her musculature until you can sink your fingers into her squishy royal ass.
With her radiant tail she shields your exploration from the crowd who, with the exception of that jerk that bumped into you earlier, are all keeping a respectful distance.
You tug at her ass cheek, pulling flesh until you find the dainty swell of her anus and vulva. You find her 'ponut' and press on it, massaging it with your finger until it slips inside.
The princess's tail flares brightly for a moment and her pussy winks playfully. A few glances are thrown your way, but they do not linger.
You retrieve your finger and step further beneath the veil. You press your face into her equine ass, burying yourself up to the ears and feeling oddly secure under the pressure.
When you pull back for air your head is spinning. For some reason you decide to grab a cupcake, spreading the princess's ass again and pressing the pastry against her anus, twisting it back and forth and using the wrapper to keep it together until you stuff it all inside.
Celestia's wings stiffen and her mane and tail flare. "Wha— hey! What are you thinking?" she asks, flushed and flustered. Then she notices the attention she has drawn and takes a deep breath before banishing their stares with her own cool gaze.
You tuck the wrapper in her pussy and find an as-yet unopened box of goods from the Sugarcube Corner bakery, peel off a heart-shaped sticker used to keep it shut and apply it to her anus, sealing the cake inside. When you let go of her ass-cheek it slaps together with its twin and forms a tight seam.
For whatever reason you are satisfied at having complicated the princess’s evening in such a bizarre and sexual way, but you forget yourself and are casually swept-up by her wing. Pulled in front of her, you notice she is blushing heavily and has a wavy smile on her face, but her eyes…
Her eyes frighten you.
“All right you little rogue." she says, raising the knee of her left foreleg to press against your pussy through your panties. "Its my turn again."
Author's Note
Well, here you go. I combined two separate stories I was working on into one and this was the result. Just a whole lotta cake. 
