Author's Notes:

I wasn't originally going to submit this chapter, but someone wanted more so I did.

Contains messing near the end. Also, quality might be lower cause I initially just wrote this chapter for myself.

Twilight was running five races with the other princesses, the annual Princess Race. Twilight was wearing her usual sports outfit (or one of the identical ones), Celestia was wearing a sparkly blue midriff tank top and matching skintight shorts, Luna was wearing something similar but dark purple, and Cadance was wearing something similar to Twilight with a white shirt and cyan shorts.

They had just finished their fourth race. The first was in Canterlot, of course. The second was an aerial race in Cloudsdale. The third was in Las Pegasus. The fourth was in Vanhoover. All four princesses were tired and sweaty. So they drank lots of water.

To save energy for their races, they rode chariots. Twilight rode a chariot with Celestia toward their fifth race in Manehattan.

They were about halfway there when Twilight accidentally farted loudly. She looked at Celestia and blushed profusely, afraid she'd call her out for being unladylike as a princess, or farting in her presence. Forgetting her reaction the last time she farted in front of her.

Celestia chuckled. "Don't feel ashamed, Twilight. Even us princesses fart sometimes." Celestia let out a loud, deep-pitched fart of her own. "I was holding that in since last race ended." She giggled.

Twilight felt reassured. She farted a few more times, much more at ease with this now that she knew Celestia thought it was funny.

About three quarters of the way there, Twilight stopped farting, but she was suddenly feeling an urge to pee. All the water she drank after her races to stay hydrated had gone through her.

"Celestia, I have to go to the bathroom," said Twilight.

"We'll have to go straight to the racetracks," said Celestia. "But we can go after the race. Think you can hold it that long?"

"I... I hope so." Twilight crossed her legs.

"Besides, it'll motivate you to run faster."

Celestia did have a point there.

They arrived at the Manehattan racetrack and stood in position.

The race began. They could only run on hoof this time. Twilight ran faster than before, desperate to finish and find a bathroom before she wet herself in front of hundreds of ponies.

Celestia had won three of the previous races, and Luna had won the Cloudsdale race. But Twilight was pulling ahead of the other princesses.

She finished first. She panted, dripping with sweat, and did the pee dance while the other princesses crossed.

"And the winner of the Manehattan Princess Race is Princess Twilight Sparkle!" said the announcer.

Twilight hid her desperation as she claimed her trophy. She drank a whole water bottle. She had no choice - she was thirsty and sweaty.

She ran to the nearest bathroom, but to her dismay it was lined up. Twilight got back onto her chariot with Celestia and they took off for Ponyville.

Celestia was about to ask Twilight whether she felt better when she saw that Twilight was sitting with her legs crossed tight, fidgeting with a pained expression on her face.

"Don't worry, we'll be at Ponyville soon," said Celestia.

"How do you... urgh... not have to go to the bathroom?" groaned Twilight.

"I do," said Celestia. "My sister and I have slightly bigger and stronger bladders than other ponies."

It was a little windy today so there was some turbulence in their trip, making it bumpy and making it harder for Twilight to hold it in.

They were just flying over Hollow Shades when Twilight lost control. She started peeing herself, soaking her skintight shorts. The pee pooled around her butt and dripped off her seat of the chariot and onto the floor. She blushed beet red. Part of her did enjoy this, but she was mortified at wetting herself in front of Celestia. Celestia stared at the purple pony as she finished peeing, and sat there in her wet shorts, red in the face and tearing up a little.

"It's all right, Twilight," said Celestia, putting her wing around Twilight. "Everypony has accidents sometimes."

"But I peed all over your chariot," said Twilight.

"So did I a few times." She suddenly groaned and crossed her legs. "I think today might be the next of those times. But I'll hold it till I get back to the castle. It's a good challenge to my ability to hold it, and if I can't... I don't really mind that much." She giggled, and Twilight felt better.

Then Twilight farted again. Both she and Celestia giggled.

As they got closer to Ponyville, Twilight's farts became wetter, dirtier, and stinkier. As Ponyville came into view, Twilight groaned from the intense pressure in her bowels after a particularly wet fart.

"Try to avoid making a mess in my chariot," said Celestia. "Trust me, it's not pleasant to clean up." She winked at Twilight.

Twilight sat fidgeting with a different kind of desperation than last time as the chariot arrived at the door of Twilight's castle.

"Sure you don't want to use one of the castle bathrooms?" said Twilight.

"I'm fine," said Celestia. "Go and find a bathroom. And try not to feel too ashamed if you don't make it. You wouldn't be the first princess."

As Twilight stood up, she let out a sloppy wet fart, and felt a bit of poop plop into her shorts. She blushed and giggled nervously. Celestia also giggled and slapped Twilight's butt lightly. Twilight took the hint and ran into her castle while Celestia's chariot took off back into the air and headed for Canterlot.

Twilight ran through her castle toward the nearest bathroom.

"Hi Twilight," said Spike as Twilight ran by him.

"Hey Spike," she said quickly. Just as she was in front of the bathroom door, she couldn't hold it anymore. Twilight farted again and made a mess in her shorts. She could feel it was hyperscat. She blushed with embarrassment at accidentally messing herself.

"Why the long face, Twilight?" said Spike. "I thought you liked messing yourself if no one else but me was around."

"You're right." Twilight giggled, enjoying how wet and dirty her shorts were. She closed her eyes tight, raised her behind slightly, and noisily released another mess into her shorts, what hyperscat she had managed to hold in several seconds ago.

...

As Celestia's chariot made its way to Canterlot, Celestia sat fidgeting with her legs crossed and a pained expression on her face, as Twilight had done earlier. Just as Canterlot came into view, Celestia started peeing. She let out a sigh of relief, and then giggled at how much she enjoyed the warm wetness soaking the crotch and butt of her skintight shorts.

...

Once Twilight had finished having fun in her wet, heavily soiled shorts, she dumped her mess into the toilet and had Spike give her a bath. She made sure Spike spent extra time scrubbing her butt. Which he loved, finding it to be funny.