"Come on, Cream!'
The light quick, and crinkly pitter-patter of tiny feet throughout the Rabbit residence made itself clearly known as the two infants currently taking residence made themselves clearly known.
They were, of course, Cream the Rabbit and her friend, Amy Rose. One was a young lass of three years, clad in a green and white frock, orange tutu-esc skirt, a pair of sneakers, and a soft, pink pull-up with floral prints that wasn't as thick as what she was used to due to the toils of rather laissez faire means of potty training. The other was around one...even if the seemingly needlessly large amount of padding hidden under her purple onesie and the booties she wore made her look and seem much younger as a result. Both were currently under the watchful eye of one Blaze the Cat, who was watching over the two while Ms. Rabbit was out on...er..."special" business.
To catch one up to speed, the two had just been in the middle of an excellent tea party just after an admittedly large lunch, and Amy had started to feel the occasional tummy grumble obviously signifying a soon-to-be-fulfilled need to go potty. Not wanting to leave out hr friend on her own, Cream was now Amy's tag-along for a one-way trip to the bathroom.
They soon make it in, Amy leading the path clearly. They stop once they arrive within the chamber of the porcelean throne, closing the door behind them. Amy gives a good look at Cream.
"Okay, Cream? I just gotta use the potty, and then we can get back to tea, okay?"
Cream, admittedly, looked slightly uncomfortable, fidgeting somewhat.
"Okay, I'll be-"
Cream grabs Amy's arm before she can work her way up onto the potty.
"Amy?"
"What, Cream? I gotta go-"
"Potty."
"...Potty? Cream, do you have to go, too?"
Cream nods.
"Well, you can go, Cream....sorta. I mean, you're still in diapers all the time. You can go whenever you want!"
Cream smiles, still trying to hold back slightly. Amy tries to head up...only for Cream to grab her arm.
"Cream, I-"
"Watch me potty!"
The baby bunny took an awkward step back, it accompanied by the light crinkling of her padding, and got ready to brace herself for what she was just about to expel into her Pampers. 
A smile of relief widens over Cream's face as a light, continuous trickle of pee started to flow into her diaper, its' new gradually appearing yellow hue obscured by the light pink fabric of her onesie. The firm, cushy padding gradually starts to break down into a warm bundle of squish taped around her waist, quickly chugging the rabbit's urine and swelling at a decent pace, althewhilst a slightly muffled hissing could be heard from within. It grows to a decent size, nearly hitting the tiled floor of the bathroom as its' tapes (and the onesie trying to contain it) strain due to the bulbous mass currently attached to the overgrown baby.
Amy takes a step back, both in simultaneous shock and awe at how swollen the thing had gotten. I mean, she tended to do a number to her diapers (or so she heard her mommy say every so often), but this was...just...wow...
She takes a crinkly step towards her younger peer, looking curious.
"...You really did have to go potty, didn't you? Your diaper's all-AHH!"
A finger on the verge of poking the squishy, sodden padding reels back as Cream clenches her fists and hunches over slightly, a grunt with clear effort behind it coming from the bunny. Almost immediately, a loud, muffled fart emerges from the ironically petite behind of the rabbit sounds out, blowing air into the diaper and puffing it out slightly, it's natural pseudo-inflatability hindered by the practical gallons of pee weighing down Cream's Huggies. The smell is admittedly hindered and somewhat absorbed by the thick, gooshy (former) poof, but it wouldn't take a rocket scientist to know what was going to happen next.
Cream grunts again, hunching in closer as her squishy butt starts to take an almost unnoticably brown hue as a grandiose load of poo begins to take residence in the seat of her nappy, it beginning to expand even further than previously possible. Cream continues to push, shoving more and more of the smelly brown mush into her (formerly) puffy panties. Her diaper continues to grow and bulge out, her onesie continuing to tighten as a result of her ever-increasing nappy, which had long since shot against the floor with the force of her stink with a heavy SLAP!  The onesie soon starts to show more of the overly-browned padding between the gradually failing buttons trying to hold the flap up, all before eventually popping and allowing the utter monster of a bowel movement some "space" to grow. Cream is unknowingly hoisted up higher than she could ever reach, on a seat of squishy, mushy, stink.
With one last push, the tinky bun adds one last lump to her massive mountain of mess (all contained by the bulging boulder that was now her diaper). A sigh of genuine, finished relief squeaks out from the little one as she loosens up and wriggles around in her extremely squishy seat for a moment.
"All done!"
Amy looks up at the relatively gigantic mushmound, backing up near the bathroom door to get a better sight of what had happened to her friend. Words couldn't describe her face upon the sight...and the smell...
"Cream? Are you still there? I can't see you!"
Faintly, her rabbit partner-in-crime chimes in.
"Boom, boom!"
Amy walks closer to the amazing colossal diaper, putting a hand in front of her and on the massive wall of mess, it pushing in slightly.
"...Yeah...boom..."
She pulls the hand back and towards her chest, it leaving a clearly visible indent onto the darkened padding and slowly filling back in.
"Hey, Cream?"
The bunny, clearly distracted by the squishy seat strapped to her sides (and not the noxious aroma, surprisingly), tries to look over the massive lump currently residing below her in order to respond...to little avail. Still, her ears perk up as a means to alert Amy.
"Cream...what...how..."
Accompanied by an audible joyous squish, Cream responds.
"Cawots!"
"Carrots?...How many Carr-"
Suddenly, the audible clic-clicking of the bathroom door being opened causes Amy to immediately jerk around to see what was coming through, Cream being completely unaware of the events before her.
"Girls? Are you in here? Is Amy on the..."
Blaze's light, friendly tone drops off as soon as she sees the utter chaos her second charge had let loose inside of her Huggies, the diaper's full fullness setting Cream almost higher than she was. It looked like the girl had somehow gotten an entire drumptruck of fertilizer inside her diaper, and the smell...oh, the smell made her reel back almost instantly, almost on the verge of gagging. Her eyes dart down towards Amy.
"Amy...Dear...What happened?"
The little girl backs up into the baby's pamps, her back against the moosh like a man against a wall at gunpoint. She looks up at Cream, still content with the massive bowel movement that had just erupted prior. She looks back at her babysitter, the purple cat clearly trying to take in the fact that she was going to have to change the mother of all stinky shorts. Her heart sinks...
And in that moment...Amy didn't need to go to the potty anymore.