"Make Amber incontinent. She can deal with it better than me," Madison declares.
"Well, if you're sure about that," you say to her with a sly smile. "Okay then. ~You are no longer incontinent, and have full control of your bladder and bowels~" It takes a couple more seconds of eager waiting from Madison before you remember she can't actually hear your orders, "Oh, sorry, all done. You can take that diaper off, you won't be needing it anymore."
"All right!" she shouts triumphantly, tearing off the diaper and going to her dresser to find a clean pair of pants to wear.
After Madison finishes getting dressed, you open the door and yell, "Amber! Come in here a minute!"
Amber walks into the room, completely oblivious to what's about to happen to her. "Hey, what do you need? And why isn't Madison wearing her diaper?" she asks, looking over at her sister in confusion.
~Madison doesn't need to wear diapers anymore, and you will forget that she ever did once she was first potty trained~ you begin, deciding it would be more fun to start fresh, ~You will also not notice the dirty diaper on the floor~
Amber stands there for a moment, her eyes readjusting towards you. She then says in a slightly impatient tone, "Okay, seriously, why did you call me up here?"
"Just wait there a second," you say. Madison is watching both of you intently, and you decide not to keep her waiting any longer.
~Amber, you now have absolutely no control over your bladder and bowels. You will urinate and defecate in large and regular episodes, with no ability to stop them or feel the need to do it~
You guess that Amber, unlike Madison when you did this to her, had not gone to the bathroom recently. Said hunch is proven correct when, only a couple of seconds later, a dark wet spot begins forming on the front of Amber's pants.
You are about to point it out, but Madison beats you to the punch, "Eew, Amber! You're peeing yourself!"
"What?" Amber says in confusion. She looks down at her crotch and gasps, "OH MY GOD!" She squeezes her legs together and presses her hand against her crotch, but she's unable to stop the flow as it continues down her leg. Eventually, Amber stops peeing, leaving a massive wet area on the front of her jeans.
"I... I couldn't stop..." Amber says, deeply embarrassed, "I... I need to clean this up. Excuse me." She starts to make her way to the bathroom.
"Hold on a second," you say, going over to Madison's drawer and pulling out another diaper, "This may be kind of tight on you, but you should probably wear it until we get ones that fit you, just to be safe." Madison tries and fails to hold back giggles as all of this is going down.
"What the hell?" Amber says in shock, "I'm not going to wear a diaper! I just had an accident is all!"
"Without realizing it," you add, "You should probably let me put it on you, just to be safe."
"Yeah Amber, he's just trying to get you cleaned up and comfortable," Madison says, clearly reveling in the roles being reversed from earlier.
"No way!" Amber shouted back, "You're being ridiculous! I'm going to get changed and cleaned up, and then I'm going to tell Mom and Dad just how crazy you two are being."
She starts storming off towards her room, presumably to grab a pair of pants and underwear to change into.
"Aren't you going to stop her?" Madison asks you as she begins following her sister down the hallway.
"No, I have a better idea," you say with a mischievous grin, "I'll make sure she has to come to us."
You wait in the hallway until Amber comes out of her room. As she walks towards the bathroom, you issue a new command to her, one that you wish you had thought of when you were messing with Madison.
~You are no longer able to change your own underwear, whether they are panties, diapers or anything else. No matter how hard you try, taking them off and putting them on by yourself is now simply beyond your ability. You are also no longer able to clean yourself up, especially if you soil yourself. If you attempt to do so on your own, you will simply make a bigger mess instead. Only Madison and I will be able to change your underwear and clean you~
By the time you finish speaking, Amber makes her way into the bathroom and slams the door shut. A second later, you hear the lock click into place.
"Whatever you did, it didn't work," Madison said with a pout.
"Oh ye of little faith," you tease, "You should know better than that. Just wait. It might take a bit, but she'll come out eventually."
While Madison waits outside the bathroom, you go downstairs to talk to the parents again.
~Amber is the one that needs to wear diapers, not Madison. Madison and I will be taking care of her together, and if Amber needs to be changed or cleaned up, you will wait for one of us do it and refuse to do it yourselves. You will both accept this happily, and be willing to leave Amber in whatever state she's in until Madison or I can get around to her~
You point to the mom again and say, ~Go back out and buy diapers that will fit Amber, as well as some powder and baby wipes.~ When she leaves to do so, you head back upstairs and towards the bathroom door.
"How's she doing?" You ask Madison as you walk up.
"Not good, by the sound of it," she says. A second later, you hear Amber swear and bump into something.
You knock on the door, "Amber? Are you ready to let us help you?"
"I can do this myself," Amber snaps, sounding upset. You hear more swearing, and hear something wet hit the floor loudly.
"Are you sure about that?" you ask in a tone of mock concern, "Sounds like you could use it."
There's no response from the other side of the door at first. Eventually, you hear the door unlock, and Amber opens it halfway. Her hair is a mess, and you see that she is no longer wearing pants, and her panties are dirtier than ever, urine continuing to drip out of them and down her legs. There are also stains on the bottom of her shirt, from where she had somehow gotten the idea to rub it into her soiled panties for whatever reason. The smell starting to come out of the bathroom makes you suspect she might have pooped herself a little as well.
"I... I need help," she sniffles, looking absolutely pathetic, "I can't get these things off. And everything I try is just making things worse."
You think about it for a moment, then decide to...