Idea.
Ever since you got locked in a house with a ghost, you seem cursed to randomly get a bout of diarrhea, and every now and then while you run to the bathroom, a bunch of bad things happen.
You wake up shitting your bed, and you get diapered, then you can get spanked later that day in the diaper position. With your diaper hanging out from between your butt and your mom's lap. Your lower back on her thigh, her off hand holding your ankles up and her other slapping your butt, which zooms around above the unfolded diaper, as your reflexes make you twitch and twerk and cringe, all in front of your school at school.
How does it happen?
Just when she isn't looking, a classmate on a skate board zooms by, listening to headphones, bumps into a girl who drops something. Maybe a volley ball or a helmet or whatever, which bounces and knocks into your mother's ankles. Or maybe into your own. Perhaps just when walking down the stairs in front of your school. So you trip and fall. Spinning as you stumble down several steps, your legs in the air, your skirt flung up, someone tries to help but they only make it worse. He catches your ankle, or knee, so you fall like a pendulum and hit the back of your head or land on your ass, instead of falling more staight down it's with torque! This makes you smack down into her. She gets up.
She grabs your arm by your shoulder and walks you to a bench in front of your school, sits down, pulls your skirt down and tosses it in her purse, so everyone can see your diaper, she then yanks you down by your shoulders, pushes you down so your back is on the bench, holds your ankles up, and yanks your butt unto her thigh.
She undoes your diaper so it's on her lap, clearly visible beneath your butt from pretty much any angle, and begins slapping your butt.
You can't stop yourself from pushing put a turd from the stress and she sees it steadily poling thru, so she pushes your ass sideways with the hand she spanks with and wraps her other arm around the back of your knees to grab your belly, and holds your butt over like she's pouring water from a barrel, then uses a doggy bag to pick up the poop.
So you can only cry there, standing bottomless, for a moment while she isn't spanking you after you poop. But someone throws a football at the back of your head so you step in it, and she doesn't see that because it's when she's reaching in her purse for the poop bag.
She thinks you stepped in it on purpose to make her made so she uses your diaper to clean your foot, and makes you hold your diaper as she marches you to the trash can to toss it away.
