One night, the girls were all having a sleepover at Rainbow's house. Sunset had not yet changed into her pajamas, and was wearing a black T-shirt and short, tight jean shorts.

"Want to watch the new Daring Do movie?" Rainbow Dash asked.

The girls all made sounds of agreement. Before picking out the movie, Rainbow got Sunset a garbage bag and a towel.

"Better make that two towels," Sunset said with a smile.

After getting her a second towel, Rainbow got the movie and put it in while Sunset picked out a spot on a couch, set the garbage bag on it, then placed both towels on it and sat down. She knew precisely what they were for and she intended to make use of it. She had already drank a lot of cider earlier.

About halfway through the movie, which Sunset was really enjoying, she needed to pee. She waited until she really needed to go, then unabashedly let go. The sound of her stream spraying denim could easily be heard as her shorts darkened rapidly and the towels she was sitting on became soaked, and she sighed of relief and pleasure.

All the girls turned toward Sunset and smiled. Pinkie, Rainbow, and Fluttershy giggled. They were all glad she was having fun, even if what she was doing was considered dirty and unladylike.

Sunset wasn't the least bit ashamed that she was peeing her shorts in front of all her friends. She was thoroughly enjoying herself, and she knew they didn't mind.

Twilight was blushing lightly, as she loved the sight of Sunset wetting herself in any outfit. An idea occurred to her, of something she really liked to do with Sunset when they were hanging out and having some wet fun. She whispered into Rainbow and Pinkie's ears. Both of them smiled.

"Hey, Sunset, next time you have to go to the bathroom, let me and Pinkie know," said Rainbow.

"Sure," said Sunset. She was confident they'd have something fun in store for her.

After the movie ended, they stood up, got some drinks and snacks, and talked some more. Sunset's shorts were wet and smelled of pee. Occasionally their conversation shifted in the direction of wettings, which even Rarity found to be a fun subject, though she still wouldn't wet herself unless she was far from a house bathroom and was sure she wouldn't make it. However, there were times the other girls were sure she peed in the water with them. She would just blush and giggle, though farting in the tub was still a lot more embarrassing for her.

Eventually, the urge to pee returned. Sunset was about to sit back on her wet towel and pee again when she remembered what Rainbow said, and walked over to her and Pinkie. "I have to go to the bathroom again," she said, holding herself.

Rainbow and Pinkie walked on either side of Sunset and started tickling her armpits and sides. Sunset started laughing hard, and before she knew it she was peeing herself uncontrollably. Her shorts became soaked again and the pee flowed down her legs in torrents and formed a large puddle where she stood. Sunset was really enjoying this, and kept laughing as she peed.

Rainbow and Pinkie stopped tickling her ten seconds after she finished peeing. "Did you like that?" Pinkie asked.

"I loved it," Sunset said when she caught her breath. She felt her wet shorts, sighed of pleasure, and sat in her puddle.

Twilight loved the sight of this as well.

"Twilight does that to me sometimes," said Sunset. "It's just as fun as peeing voluntarily."

"I thought you two might enjoy tickling her into urination," said Twilight. "Plus I get a good view of it this time."

"We sure did," said Rainbow Dash. And why shouldn't they? They thought it was funny to see someone pee herself and they knew Sunset liked it.

"I take it you don't mind me peeing all over your floor," said Sunset.

"I don't mind cleaning it up if we can get some fun for both us and you."

Sunset let out a sputtering wet fart in her puddle.

"Sunset!" said Rarity while Rainbow and Pinkie laughed and Twilight blushed.

"Excuse me," said Sunset.

"Like you're one to talk, Miss Bubbles in the Tub," said Rainbow Dash.

Rarity blushed. "Oh, it's quite all right, Sunset. If I can put up with Rainbow Dash and Pinkie Pie breaking wind..."

Rainbow and Pinkie giggled, and so did Rarity. She hadn't been super-offended, it was her natural response whenever she heard someone fart. She did at least like to keep up something of a ladylike image despite how often she would wet herself and fart in the tub.

When Sunset stood up, Rainbow cleaned up the puddle and they got on with the sleepover.

Sunset stayed in her wet shorts until it was time to go to bed. She changed into her pajamas and climbed into her sleeping bag.

...

"Sunrise and shine!" said Pinkie.

Sunset woke up. It was morning. She looked around. The other girls were all awake and dressed for the day.

"Did you have a nice sleep, darling?" Rarity asked.

"Yes," said Sunset. "I dreamed that I was looking for a bathroom, even though normally I'd go in my pants, but there was always someone around or the stall or toilet was missing. I guess when I have those dreams I still get in the mindset to avoid wetting myself, but I find it fun now. Although, when I did find a toilet, I remembered, and peed through my pants into the toilet, so much that the toilet overflowed. Then I woke up."

"Did you wet your sleeping bag?" Applejack asked.

"No, but I still have to go to the bathroom really badly."

"You can go right there if you want," Twilight said.

Sunset smiled.

Ssssssss...

"Ahhhhhhh..."

The other girls giggled, and Sunset knew they meant nothing by it. Once again she felt absolutely no shame, only pleasure.

She stayed in her wet sleeping bag for a little over ten minutes before she got up and changed into her damp shorts, which still smelled of pee.

Author's Note

I couldn't resist referencing Rarity farting in the tub, since her pony counterpart legit does that in the comics. (Nightmare Rarity arc, alluded to by Pinkie in Part 3 (Issue 7) and shown in Pinkie's flashback as her fondest memory of her in Part 4 (Issue 8).