Optional end screen hours later with a much fuller diaper and the guy exhausted from cumming.

Caretaker comes out to see him slouched over his own diaper, both hands over an erect dick. She rolls her eyes and says, "we've talked about this, that's disgusting. If you love your poopy diapers so much then you can just stay in that one all day. See what I care about the smell."

He tries to power through it and makes it to the stairs, which prove VERY difficult because of the extended leg movement. One tender step after the next he edges closer, until his mom yells at him again, causing him to jump. The poop bounces, and one good rub sends him over the edge.

Oh forgot to mention, he's gotten in trouble for cumming in his diaper without permission, so he's basically just a ticking time bomb trying desperately not to go off. But then his caretaker demands he get a move on or else... something. So he's forced to walk faster.

his caretaker/changer yells that it smells bad and he needs to go upstairs for a change right away. He immediately stops what he's doing embarrassed, but still hard as diamond. As he walks, the poop is still squishing and he has to take very small, deliberate steps in order to make progress.

I've had this idea for a bit

Guy is just laying around doing nothing when he suddenly has to poop his diaper, so he does. He doesn't seem to mind and just goes about his day, until the poop goes up the front somehow. He poops again somewhere in her and starts getting off on the mush. But then...