Warning: This chapter goes further than I have before, and includes diaper messing content and bondage.
Princess Peach was in a good mood. Sure, she had recently been cursed by one of Bowser's minions to be unable to change herself, leaving her to be totally dependent on others to change the diapers she wore to handle her bladder problems, but more importantly than that, today was the day that she got her revenge on a friend who had gotten one over on her too many times. She wanted her friend Princess Daisy to join her on a trip she had planned, but as the situation was now, with Daisy having pranked Peach mercilessly in the past, their relationship was too uneven for Peach to feel satisfied. Her trap, she felt, would change all of that.
There were a few things that Peach and Daisy always did when they met. Both of them had somewhat of a sweet tooth, and they'd always gift each other with some good food to mark the occasion. This time though, Peach had laced her gift with a bit of a laxative surprise.
Peach invited Daisy to her castle, and was there to greet her when the carriage rolled in that evening.
"Good evening, Daisy! You must be hungry after your long trip, so I had some cake prepared for you."
"Perfect!" replied Daisy gratefully, "I'm always a fan of your cakes. I brought some of those sweets from our kingdom that you like so much too, so let's get right to it!"
They walked into the castle, where the Toad servants had set up a proper table with a slice from one of Peach's famous homemade cakes set up for Daisy, and in return Daisy handed Peach a small bag of sweets and each got to work on the food, which in Peach's case involved eating daintily with all her table manners remembered, which wasn't always the case for Daisy, who had always had an independent streak and leaned more towards being a tomboy at times.
Peach smiled at Daisy, both with satisfaction at the food and because Daisy, not suspecting anything from the usually straight-laced Princess Peach, had eaten the entire slice of cake, and even gone beyond expectations to ask for a second slice. Now it was time to initiate the next phase of the plan. The nervousness was making her feel a bit queasy, but it was nothing she couldn't handle.
"By the way, I have something to show you", mentioned Peach. "I think you'll find it quite interesting". She lead Daisy down the stairs and further down into some of the lesser used areas of the castle. Some former inhabitants of the castle had given it a dungeon, but it wasn't used nowadays, so it was quite empty and also quite perfect for what she wanted to do. She closed and locked the large wooden door of one of the dungeon rooms and gestured to Daisy that she should take a look at a hole on the far side wall which seemed to open out into another dungeon room opposite, open at about shoulder height.
"Poke your head in and tell me what you see", suggested Peach. Daisy leaned forward into the hole, and at the same moment, Peach pulled on a lever and the trap snapped shut. Daisy was now trapped leaning forward, her head in a wooden stocks which had been carefully placed and trialled by Peach the day before. The rest of her body was now helplessly stuck in the same room as Peach, who lifted up the back of Daisy's dress to reveal her smooth white legs and frilly orange panties, which had a big yellow star emblazoned on the rear.
"You see, Daisy, you are not the only one who can play tricks. That slice of cake you ate included the extract of a very rare poison mushroom. It's not going to harm you, but as for your control down here," Peach took the chance to give Daisy's crotch a gentle rub from the front to back, "it's going to be a week before you recover, after all the cake you ate. Maybe from now on you'll think about the way you've treated my situation."
Daisy squirmed and shouted and struggled, but it was no use. The dungeons had been designed to absorb noise, and the only one able to hear her pleas, Peach, had no intentions of helping. Peach was dealing with her own problems - she was glad that Daisy couldn't see her, because she was squirming herself. Her queasiness from earlier had only gotten worse and even though she'd already wet herself somewhat during the trip down, it hadn't soothed the symptoms at all. That was fine though, she could deal with that after she taught Daisy her lesson.
"It's been about 15 minutes now, and I can see that you're already reaching your limit, Daisy. I'm a kind person so I'm going to give you a choice - would you like to go in your panties as they are, or would you like to be fitted with a diaper like I wear?"
Daisy murmured something, but couldn't seem to find the courage to say it clearly. She loved pulling pranks herself, but she liked to be in charge and this situation was entirely the opposite. The idea of her unable to control her bladder and bowels in front of someone else was thoroughly humiliating to her. However, pride could only take her so far, and her needs were getting more urgent by the minute - she could barely contain herself as is.
"Speak up, Daisy, I can't hear you", giggled Peach.
"Please, give me a diaper", Daisy cried out more loudly, her spirit finally broken as her body shook from trying to hold back the inevitable.
Peach tugged Daisy's orange panties quickly off, tossing them to the side, and got to work with the diaper she had ready. Due to the curse she couldn't change herself anymore, but the skills of a lifetime of wearing a diaper were still there to change Daisy with. With the garment finally in place, the comfort of knowing it was there meant that Daisy finally made the mistake of relaxing for just a second. She tried to stop herself but it was too late. Her body spasmed as everything tried to escape at once, and the diaper swelled as she uncontrollably wet and messed herself, crying as years of self control went out the window as her friend watched her lose the last shreds of dignity she had left. When the last of it had ended she slumped, her energy all spent and too exhausted to move.
Peach pulled the lever back, and finally Daisy was released from the control of the stocks. She fell onto her rear with a splat, and lay there on her back, staring at Peach with an unfathomable expression. Finally, she managed to quietly say "so how's your diaper, Peach? You've noticed by now, haven't you?"
Suddenly the realisation struck Peach. The reason she had felt queasy since she had eaten wan't because she was nervous about this plan, it was because Daisy had prepared a surprise of her own. It wasn't as fast acting as Peach's cake slices, but it had become increasingly hard over time for Peach to stop from messing herself as she waited for Daisy. She at least wanted to win this fight by doing it somewhere that Daisy couldn't see. She walked carefully towards the door, but quickly realised that she had locked it when they had come in. Where had she left the key?
Ah, there it was, in the corner on top of a small pile of straw. She crouched down to pick it up and too late realised her mistake. The disaster she had avoided while in a standing position was just too much for her body in a crouching position, and her body let loose a huge wave of mess into the diaper. Losing her balance, she fell onto her rear and could only lie there shaking as everything from the last day was evacuated right into her now bulging diaper.
In the stunned silence that followed, Peach thought about it all - how she had planned it all out, how she had gotten her revenge, and how in the end it had all ended up right back on her. The situation was so absurd, that in the end all she could really do was laugh. Daisy started to laugh too, and that only made Peach laugh harder, until there they were, lying on the floor in diapers filled beyond capacity, laughing hysterically at something which objectively speaking wasn't very funny.
Daisy stayed the next week in the castle, still recovering from the poisoning, and experiencing a bit of what life was like for Peach. In the meantime, Peach explained everything that was happening - that she had been cursed, that she needed friends for a quest to fix the problem, and that she wanted Daisy's help. Daisy, who couldn't exactly stay mad at a friend who had only pulled the same trick she had, was agreeable and they decided that before they took off, there was one more person they needed on their trip. It had been a while, but it was time to go see their friend Rosalina.