Author's Notes:

Done by a very specific request that might be more than a bit of a stretch. If anything in it contradicts previous chapters involving Sunset, think of it as an alternate universe. Besides, by request this chapter contains fat, which isn't one of my fetishes.

Sunset Shimmer was constipated, probably from something in the big meal she had eaten recently.

After about a week, she realized something was wrong and took laxatives, but for some reason they didn't work. A week later she went to the doctor, who told her to wait it out.

Sunset was unable to pee or poop for two months straight. In this cartoon world, this wasn't painful or anything, but it did make her really fat. Fortunately her orange skirt was stretchy enough to accommodate her new size, as was a black tank top she had, and most of her underwear.

She had gotten back together with Flash Sentry, who didn't mind how fat she had gotten.

Before she knew it, it was graduation day. Sunset was still constipated and still fat, but, under her orange skirt, she was wearing a sexy pair of pink panties that were lacy around the edges, because she wanted to have fun with Flash that night. She liked how tight they felt even with how much they could stretch over her fat butt.

The school served a mexican buffet as a treat for the seniors, and Sunset pigged out, before drinking a bottle of soda. Her panties felt a little tighter on her.

Then came the graduation ceremony. As Sunset sat next to the other girls and Flash Sentry, she suddenly let out a wet fart.

"Excuse me..." Sunset blushed.

As she was called onto the stage to give a big speech, Sunset farted a few more times. The audience laughed, but Sunset tried to ignore them and continue her speech.

As she continued to speak, Sunset's farts got wetter and wetter. Even Celestia, Luna, and the teachers were laughing. Sunset blushed, but ignored them and continued her speech as though nothing happened.

Then, all at once, desperation hit. Her constipation was over. The mexican dinner had reactivated Sunset's bladder and bowels. But this was the worst possible time for it to happen!

She started squirming, desperate to pee and poop, but she had to finish her speech first. Then she could find relief, although whichever toilet she used would probably be out of order for months.

Her speech was about halfway done, and as she spoke, she became more and more desperate. She let out a fart to ease the pressure, but nearly soiled herself there, and knew that next time it wouldn't be just a fart. Meanwhile, she crossed her legs and fidgeted harder, for she had to pee just as badly. She had never known desperation like this before. After all, she hadn't gone to the bathroom in two months.

Soon, she was almost done her speech, and she was about to burst.

And just as she was saying the last sentence of her speech, she did.

PPPPPPPBBBBBBBBBBLLLLLLLLLLLRRRRRRTTTTT!

*pssssssssssssss*

Sunset blushed beet red as everything she had been holding in burst out of her at once. Hyperscat noisily made its way out of her butt like there was no tomorrow, and she started to pee, wetting her panties and the front of her skirt.

Only ten seconds in, her panties overflowed, and her poop oozed out of her panties and onto the floor behind her. In view of the whole school.

The audience erupted into laughter. Rainbow Dash and Pinkie Pie wet their shorts from laughing too hard, while Rarity looked disgusted, but felt bad for Sunset, as did Fluttershy.

As Sunset continued to pee and poop non-stop, she slowly began to deflate. But she wasn't aware of this, still too humiliated at her accident. She tried to stop, but she couldn't.

And it wouldn't stop coming out! She was releasing two months of piss and shit. The relief felt wonderful, but it was so embarrassing to do it in her underwear in front of the whole school.

It kept coming out, and her puddle of pee and pile of shit grew by the second.

Finally, after just over seven minutes, she was done. She had deflated back to her slender, sexy self, but her panties were filled with poop and soaked with pee. Not to mention the front of her skirt was wet, her legs glistening with pee, and she had a stain on the butt of her skirt. And she was standing in a massive puddle, with an even bigger pile of poop behind her.

She blushed and giggled nervously, letting out a final fart.

...

"Come to my place and I'll get you cleaned up."

Before Sunset knew it, she was at Flash Sentry's house. She smelled really bad, but he didn't care.

"You must have really needed to go."

"I told you, I haven't gone to the bathroom in two months. I guess that Mexican buffet did the trick, but..." She blushed.

"It's all right. One little accident isn't going to come between us."

"I'd say that was more than a little accident."

"All right, one big accident. Besides, you did look kind of sexy wetting and messing yourself like that."

Sunset blushed for completely different reasons. "You think so?"

"I know so."

"It's a shame I ruined my panties I wanted to surprise you with tonight."

"Show me."

Sunset turned around and lifted her skirt, showing Flash her soiled underwear, which was still moderately tight on her even after having been stretched from when she was fat.

"Whoa, sexy panties!"

"They'd be sexier if they weren't full of poop."

"If anything that makes them even sexier."

Sunset giggled, no longer ashamed of her accident, and she and Flash kissed.