Being the jealous sort and tired of losing to Harry in just about everything, Draco had combed though all of his uncles potions text books and finally found what he was looking for, a luck potion. With this in his system there was NO way Potter would beat him at anything, be it a wizards duel, a quditch match or even at wooing the pants off of a girl! (of course if Draco had known Harry played for the other team so to speak, this might not of been a concern.)
That said it turned out the potion wasn't as easy to make as he thought between the work that went into it and then of course getting the indigents as well. More then once he'd been given a lecture about respecting someone else's stuff by his uncle Snape but since he was Snape's favorite nephew he'd been able to turn on the puppy dog eyes and get out of trouble.
Still the end result didn't look anywhere near like the picture, but Draco knew he had pushed his luck (ironically) so there would be no second chance at this unless the potion worked. 
the thick brownish sludge tasted pretty much like Draco had expected and he gagged horrible as he finished it, stumbling out of the closet where he had been brewing it and coming eye to eye with his uncle. 
Snape looked over Draco's shoulder and grimaced as he say what his nephew had brewed and curled a lip. 
"Please tell me you didn't actually do what I think you did you remarkably stupid boy." He said, in a voice that made it clear he already knew the answer. 
"If I said no...would you believe me?" Draco asked, trying to hold back a gag. 
"Well Let me put it to you this way. When I realized WHAT you were trying to do I might of mislabeled some of the stock in my storeroom. so instead of a luck potion you just brewed something meant to induce 1 week of total incontinence." Snape said with a smirk.
"...1 week if I drank the whole thing?" Draco squeaked out, turning pale and letting out a foul tasting belch. 
"One week per douse...I think we better go get a certain naughty little boy in his nappies." Snape said and chuckled. 
"U-Uncle Snape! you can't! there has to be a counter t-" Draco whined, shaking his head. 
"There is and no I won't be giving it to you, you made your bed now lie in it. be thankful I'm not making you enjoy the rest of your 'home brew'..looks like there was a enough there to leave you in nappies for 2 months."
As Draco started to bawl the back of his knickers started to fill out and Snape quickly realized he wasn't cut out to handle his nephew's punishment..but that didn't mean he didn't have someone else in mind.

"So..let me get this right.. You'll stop taking house points off of griffindore unfairly..and in return.." Harry was saying, as he stood in front of Snape's desk. 
Behind and to the side was a sight that despite what Harry had been told would be expected of him, brought a big stupid smile to his face. 
Draco Malfoy in a massive white nappy, sitting on a green blanket and in a white tank top..and sucking on a dummy while looking anywhere but at Potter or his uncle.
"Yes, you'll spend the next week looking after Draco and changing his nappies. You don't have to but I'd also like to encourage you treat him like the stupid infant he's proven himself to be." Snape said, getting a LOUD whimper from Draco.  "Honestly, I only let it go this far to teach him a lesson but between the smell." anther whimper. "and the large output." MASSIVE whimper. "I've come to realize I'm not up to the task.I was going to pick one of the Wesley's for this but then Draco insisted on you." 
"heh, I see~" Harry said and locked eyes with Draco, who went from a moment of triumph thinking about how potter would be forced to wipe his behind to seeing something in Harry's face that told him mistakes had been made.
"Well before I accept, I have a few questions if I may?" Harry said.
"Go on."
"Will he be coming back to my dorm or will I be spending time in his nursery..oh sorry, his room?" Harry said getting a death glare from Draco while Snape smirked. 
"That's up to you, though given the smells he lets off I think your housemates would prefer you have him stink up his own private room." Snape said chuckling. 
"Fair enough~ Will he be going to classes while in his nappies or just staying with me and making lots and lots of 'presents'" Harry asked, using air quotes as Draco whined and grumbled.
"I'll excuse him from classes and you as well. I might be a horrible cruel teacher but even I have limits to what I'll subject the whole school too." Snape said reasonably, noting that Draco was bright red in the face and rocking back and forth, a sure sign a 'present' as harry called it was on it's way.
"Alright. Last question: do you mind if I make him sit in a stinky nappy? I think having to 'savor the fruits of his efforts' for a bit will help drive the point home, plus a little bit of nappy rash never hurt anyone." Harry chuckled.
"UNCLE SNAPE! NO! I CHANGED MY MIND!" Draco cried out, clearly realizing just how mean Harry could be.
He was up on his knees and had his hands together, pleading and tears filling his eyes
"Well if you can handle the smell, then all the power to you." Snape said and then glared at Draco. "You made your crib dear nephew, now lay in it. If your anything but a good boy for Potter while he watches you I have NO troubles with reporting back to your father that you did this to yourself on purpose."
Draco's eyes went wide as could be, the thought of his father thinking he WANTED to be a nappy filling baby filling his head and the fear making him fill the seat of his nappies.
Harry watched with sadistic interest as the the back of the diaper grew bigger and a soft crackling of the plastic could be heard between the wails Draco let out as he rubbed his eyes. 
A normal person would of felt a little bit of pity for poor Draco, or been totally disgusted. 
Harry however found himself grateful for the billowing robes he was wearing as he took glee in the sight.
'Maybe the sorting hat was onto something, I should of been in sylerin.' Harry thought with a mused look, thinking about how much fun he was going to have with the next seven days.

The end