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During a fashion show of new sports outfits Rarity made for each of the Main 6, Twilight had to go to the bathroom really badly, but Rarity told her to hold it as the show was about to start in one minute. She held it in for the fashion show, but when the curtains closed with the ponies behind it, Twilight ended up peeing herself.
 
She was a little embarrassed, but relieved she didn’t wet herself onstage, and also part of her enjoyed the relief of peeing after holding it for so long, even though she was doing it in her shorts. Her friends were super sweet about it and Rarity treated her to a nice bubble bath in her soiled outfit, which Twi enjoyed thoroughly, especially the butt scrubbing, and by the time she was clean she didn’t feel one bit ashamed of her accident.
 
I couldn’t resist doing one after my last mud edit about her.