Twilight Sparkle and Rarity were playing beach volleyball. Rarity had fashioned outfits for them; Twilight's was a dark blue shirt and skintight red shorts, and Rarity's was a light blue shirt and skintight pink shorts.

After about an hour of playing, Twilight had to pee badly. "I need to use the little fillies' room," she said, and she ran off.

Now that Twilight mentioned it, Rarity had to pee too. They had both drank a lot before the game. Rarity ran after Twilight, and Twilight reached the only bathroom, which was the kind with the lockable door and only one toilet. When she tried to open the door, she found the door was locked.

Twilight paced back and forth, trying her hardest to hold it in, while Rarity sat outside, with her legs crossed. She didn't have to go quite as badly as Twilight, but she was very uncomfortable.

After about five minutes, the door opened, and a pony came out. Twilight had drank more than Rarity, and she really needed to go, so she immediately ran right into the bathroom and closed the door. Rarity hoped Twilight wouldn't take long.

Twilight was halfway to the toilet when she tripped over a rock that was in the bathroom for some reason and fell flat on her face with her rear in the air. This was too much for her. Twilight peed herself, soaking her shorts and making a big puddle on the floor. She sighed of relief, but was very embarrassed, as she knew Rarity was going to find out. How could she, a princess, have wet herself like this? Once she finished peeing, she started cleaning up the puddle on the floor.

Rarity waited impatiently outside, fidgeting where she sat and still with her legs crossed tight. What was taking Twilight so long? She really needed to go now, and she couldn't hold it much longer. She walked over to the door and was about to bang on it telling Twilight to hurry up, when Twilight opened the door, slamming it in Rarity's face. Rarity fell on her side and wet herself. Despite the relief, she felt ashamed beyond belief, and let out a whimper as she kept peeing uncontrollable.

"Oh my gosh, I'm so sorry," said Twilight, blushing with embarrassment.

Rarity finished peeing. Her pink shorts were soaked and she was blushing profusely. However, she noticed Twilight's wet shorts and felt bad for her. "That's all right," she said. "Let's go for a swim in the lake, and then we'll continue our game."

Author's Notes:

I updated this chapter to add a little more detail in response to criticism about the quality. And I know this one probably seems the most rushed, I just did this to complete the set, and at the time I couldn't really think of any other scenarios with them.