She took the pebble and thought,"Eh, why not", stripped off her clothes, and shoved it up her butthole. As she put it in, she moaned sexually and started to jizz a little. When she couldn't push it in anymore she waited for something to happen. Suddenly her body started to vibrate, shaking more in her stomach. At first, her body started to bloat a little and she responded,"Woah, were my boobs always this big, and my ass feels softer." Suddenly, she let's out a small fart."Oh excuse me," she chuckled quietly to herself,"I think I'm a legal adult now. Sweet! I wonder what I'll do with this now". She suddenly felt heavier, as if she got fatter. "Why do a feel so heavy all of a sudden," she wondered. She touched her stomach and felt some cushion there and yelled,"Oh my god, how that happen, I was super skinny!" She ran into her bathroom and checked her weight. The scale read 115 pounds and that's when she started to panic. "Ohmygodohmygodohmygod, what's happening to me, I used to be 95 pounds! It must be that damn pebble." she thought as she tried to reach back into her anus. Unfortunately for her, she had dug it in so deep that she couldn't feel it at all. At that point she knew that she was screwed. "I hope I don't get too big," she prayed as her body continued to swell along with her farts. "I'm getting even fatter by the second, and I'm farting even more now! Each one smells worse and gets wetter than the last too. I need to get help" she exclaimed as she tried to run to the nearest phone with brown dripping down her thighs. She didn't get far as she tripped and fell right on her flabby stomach causing her to release a giant wet fart that lasted a good 10 seconds. "Ugh, I'm so heavy that can't even lift myself up, and that smell." she complained as she struggled to lift herself up. Suddenly a sharp pain was felt in her fat bottom half, that was followed with a very wet fart. "Ah crap, I think I'm about to literally crap. I gotta hold it in, don't want to ruin the floor, not that it's already browned," she said trying to roll on to her back to get some leverage to get up.
Then...