The grey earth pony was caught offguard as the bellows quickly ballooned to shape, only to loose a loud hiss and seemingly squeeze themselves together, pushing the first paypoad of golden-orange gas into the pegasus. Her hooves slipped free of the inflatable implement as she found herself being pushed back by the swell of his belly underneath her, only to be squished either side by hos own ballooning haunches as she settled back inbetween them, straddled across his waist. Though her vision was rapidly obscured by his growing body, the steady hiss from the small tank followed by sharp, forceful fwhoosh! from the bellows closing themselves did fill her ears, and clue her in as to what was going on. Self-actuating bellows, and fed from a tank of that golden gas no less...

She couldn't help but wonder if she may have made the slightest of mistakes just now.

My entry for Winterlight's contest, a little self-indulgent sequence. Shenanigans ahoy~