pretty much a niche fetish, i guess
 
have a story:
 
rd: “No WAY Twilight, I am not going out there like THIS, how I am going to explain that to anypony ?!”  
ts: “Princess’ orders ? That is your problem, you brought this upon yourself Dash, now deal with it.”  
rd: “T-Twilight when I agreed to your disciplinary lesson I thought you had a more literal lesson in mind !”  
ts: “Oh you mean you had a nap in mind ?”  
rd: “Eh-hehe well I guess we are long enough together that i can’t deny that and sound convincing huh ?”  
ts: “Also long enough for me to know that you secretly like this..”  
rd: “I do NOT like bein… NO wait what are you doing, put that remote awa..”  
Twilight pushed a button on her remote and the device on Dash’s back emitted a warning noise before it shot a short electric shock through her collar. ‘Beep Beep’  
rd: “Ngyaaaaahhhhhh.. Fuck, Twilight that..”  
The device interrupted Dash with a prompt response “Inappropriate profanity detected, prepare for punishment.”  
Twilight watched Dash’s eyes narrowing as the safety spell on the device checked that the Pegasus’ surroundings would be physically safe for the next step, Twilight didn’t want it to knock the Pegasus out of the air or immobilize her in any other potentially dangerous situation, so she designed this spell.  
As soon as the check was done the device applied another longer lasting painful shock through Rainbows collar, instantly followed by a couple of weaker but still quite unpleasant electrical busts delivered through the hollow anal and vaginal electrode plugs inside the pegasus.  
The collar shock painfully immobilized Dash and the second wave made her eyes bulge as her nethers flared up in inevitable, painful yet slightly pleasurable bursts, it almost knocked her off her hooves.  
As Dash’s senses came back she didn’t need to ask for the owner of the electrical powered train that just slammed into her back, her face was showing off an uneasy, surprised blushing expression, Rainbow didn’t care about her looks, what worried her was the short warm tickle and the disappearing wet spot she felt in her groin.  
rd: “f.. unng. gosh Twi i think you just made me pee myself.  
Twilight who was seemingly satisfied with this unexpected test run, gave Dashs padded back a glance, there were yet no signs to prove her claim.  
ts: “Dash you brought this upon yourself… again, I just gave you the first one to make a point, I classified this as disciplinary measure for a reason. Besides the diaper is not wet if you are worried about this, it was probably just a squirt but at the rate you are going i might have to make room for an unscheduled change today”  
rd: “ugh.. egghead only you would cl…”  
“Inappropriate profanity detected, prepare for punishment”  
Rainbows eyes narrowed again underlining an unbelieving horrified expression, before she could tense her muscles a few more drops of urine escaped into her diaper, before a pleading “No please !” came out of her mouth.  
Twilight chuckled and pushed another button on her remote, causing the device on Dash’s back to announce that the procedure would be aborted. “Oh Rainbow Dash i am so going to enjoy this month”  
Rainbow gave Twilight an thankful look, then Twilights words sunk in.  
rd: “A month ? you mean i am stuck in this for the entire MONTH ? NO !”  
ts: “Technically not the whole time, there are 3 scheduled changes a day, you better don’t miss those and maybe unscheduled ones, if i feel like it, which brings me to the occasional breaks that might happen if appropriate” Twilight gave Rainbow an unambiguous wink.
 
Rainbow was still taking in the change part and what this eventually would suggest, she also realized that the hollow electrode plugs in her nethers would make it difficult to fight it for long, then the last part of the sentence hit home and rainbow blushed as she realized that even without some kind of bondage rack Twilight now had complete control over her, a thought that without doubt turned the Pegasus on.  
rd: “S-So you designed this to make me your remote controlled pony slave ?”  
ts : “I designed this to give you a special somepony discipline lesson, the rest just came as bonus. But this brings me back to the point where we started, i believe i asked you to do the groceries and collect my order from Sofas and Quills.”  
rd: “But i can’t walk out like this ! What i am going to tell other ponies ?”  
Twilight smirked and opened the castle door with her magic, it was still rather early outside so the streets weren’t that crowded “We already went through the theory, time for the next step”.  
And with those words Twilight lifted Rainbow up and shoved her out of the door before slamming it shut again, from behind the door Twilight spoke “And don’t forget to behave out there, we may even have one of those mentioned breaks later, you are surprisingly ‘inspiring’ in this”  
“First destination Ponyville market” Said the artificial voice coming from Rainbows back.  
Rainbow was looking into the town, fortunate there weren’t much ponies on the streets by now but that didn’t mean there were none, there was no going back, she was sure Twilight wouldn’t let her back in before she was done collecting her stuff, not even for that mentioned ‘break’.  
“No loitering, you have one minute to get moving” Sounded the device again.  
Rainbow ignored it, by now the Ponies of Ponyville knew about Twilights eccentricities, most of them where constructive, although less kinky, and those that weren’t usually didn’t last long so they came to accept or at least tolerate them, Rainbow expected that ‘Princess` orders’ would indeed go a long way if she had to explain her situation, word probably wouldn’t even spread beyond Ponyville, and in a few months it would most likely be forgotten but that didn’t mean she looked forward to it or that she was cool with it in any way.  
How would she explain it to the rest of their friends .. ?  
Applejack would probably raise a brow, have a laugh and support it as long as they kept it away from her back.  
Fluttershy would probably be proud of Rainbow that she decided to go through with it, as well as sorry for the discomfort it causes.  
Pinkie Pie ? Who was she kidding she would most likely show her a similar device claiming that she wears it for fun.  
Rarity .. maybe rarity could talk sense into.. No Rarity was going on about how Twi put up with Dash’s frequent misbehavior since Twi and Rainbow announced that they were together, even if most of it was just jokingly. She would probably ask Twi to have a look at the profanity list to add a few things and might also insist on putting her into a dress or something to hide the features of the disciplinary device and currently Rainbow didn’t know which one would be worse, being forced to wear an electroshock diaper or being forced to wear it in style.  
Twilight was going to owe her for this, owe her big time !  
Dash remained in front of the door contemplating the actions that brought her into this predicament, realizing that there was no desirable way to get out of this. She stood there thinking for a while until the loiter timer reached 0.