[Princess Goomba]

Sweetie Belle just slowly nodded as her sister spoke, though she was a little disappointed that they wouldn't be going up in there, but Rarity's point did stand, Sweetie Belle was feeling a bit lethargic, riding on her sisters back hadn't made her feel any less tired, if anything she'd gotten rather cozy where she was. Though Sweetie Belle wasn't a foal, she could walk on her own! But.. She was comfy..

As she stopped to give it some thought, her body saw fit to take control away from her. "Uuhh.." Sweetie Belle said as she was deep in thought, her gaze looked towards Rarity's face, but it was clear she was not looking at Rarity, more like she was looking past, or through her, with an expression that looked like she might be going to sneeze, eyes a little tightened, face a little contorted. Her tail suddenly hitched upwards like a flagpole, pointing upwards, and forming a little curve at the top as her tail hair came back down. Her body tightened, Rarity would feel Sweetie Belle's stance on top of her stiffen.

A sudden gurgle rippled through Sweetie Belle's lower abdomen, one Rarity might have felt given Sweetie Belle's close proximity, then a slight shudder as a feeling of euphoria began to roll up Sweetie Belle's back, her previous look, one that could be generously described as her 'pooping face' fell away as Sweetie Belle began to relax, her face relaxed, all tight and contorted features softening as her eyes lidded, her ears shifting down a little. Her body also relaxed, feeling much less tight. The span of time between Sweetie Belle looking like she was going to relieve herself, and then getting there, was mere seconds, no real time for her to be made aware of her bodies next move.

The back of the fillies diaper quickly moved outwards as she pushed out a load of horseapples into it, Rarity would feel the heat of it roll across her back as it spread and filled. A few muffled bursts of flatulence came with it as the all too familiar odor of a messy diaper began to waft out from her, a pungent aroma that easily cut through the air around them. The warmth of the diaper was only intensified as Sweetie's bladder joined in, giving her diaper a much more thorough soaking, especially as it had been a bit wet before, but not in a noticeable way, it was definitely noticeable now.

Unfortunately for Rarity, given how she treated her sister to many 'extravagant' things, which included food, the heft of the dirty diapers Sweetie Belle produced were often on the heavier side, and this time was no exception. Once the diaper was filled to near capacity, at least on the solid side, Sweetie Belle let out a sigh of relief as it ended, again taking just a few moments to do all that. Simply enjoying the lovely feeling that stayed with her, though it faded after mere seconds, leaving Sweetie Belle with the distinct feeling of a messy diaper on her flank, and quickly putting things together, realizing she'd done her business while on her sisters back. While Sweetie Belle wasn't adverse to using her diapers, in this particular position she was more concerned about subjecting her sister to this, causing the fillies eyes to widen, quickly glistening. "Rarity.. I.. I.." Slight hiccuping to her voice now.