"Wait a moment..." You hear from outside of the room, before that beast makes its way back inside. You quickly gasp and hide behind a dresser full of the same boxes, leaning up against a wall as you stare across the room at the other wall, terrified and unmoving. The smell fills the room once again, and you force yourself to breathe it in so he doesn't hear you gag again. The beast stomps through the room, making you sweat heavily. You pray he doesn't walk too far into the room, and after a few moments, you hear the sound of paper ripping or shredding. After the much more intense wave of stench hits you, you realize the beast just ripped off the sides of his diaper, and hear a disgusting thud and squish as it hits the ground.
Unable to hold back, you cough and struggle to breathe, to which the beast turns to look at you, surprised and blushing with his ass covered in really gross, dark brown shit. "O-Oh! I didn't know anyone would be here..." He says shyly, and upon looking out from hiding, still afraid and coughing from the nasty smell hitting you like a truck, you see his entirety. The canine is a very, VERY large dog man, a saint bernard in a human-like form. His body is thick and wide, and his fur is fluffy. If it weren't for the nasty load of shit resting in a diaper on the ground, you'd honestly find him cute. "M-My name's Davis... I need help, there's a certain kind of... of beast briefs in here. I need another one so I don't p-poop forever...!" The big dogman says just as shyly as before, his paws behind his back and his legs crossing one over the other, then switching. By the looks of his big fat gut, you could tell he wasn't kidding. That big stinky mutt really had to go again, despite the massive load already on the ground!
Without any warning, an enormous fart erupted from his massive booty cheeks, making them clap together with each blort and blurt of steaming hot gas. It was so intense that an extremely dark cloud actually spewed into the room from behind him, slowly filling the rest of the room with a mixture of musk and stink. "I-I suggest you put one on, too, before you get knocked out..." Without much understanding of what's going on, and a sinking feeling that the VISIBLE FARTS are slowly seeping towards you... yeah, you think it's a smart idea to trust the otherwise sweet giant.
Opening yet another box, you pull out a diaper and quickly slip it on, nervously eyeing the stinky fog as it sweeps by your feet, and then slowly rises with each loud blort from the giant mutt's most likely donut-shaped butthole. The diaper suddenly clamps onto your waist, startling you and in tandem making the big dog man gasp, then fart really hard again. You glare up at the dog, who puts his paws behind his back and blushes, looking a little ashamed and tapping one foot on the floor. Looking back to the painless clamping diaper, you see fur beginning to rise up on your body. Blinking, as if there were any way to believe this weren't happening, you watch as your body morphs and changes, muscles growing outwards from your groin and ass as you slowly grow up and groan. A tail bursts out from just above your ass, slipping perfectly through the hole you didn't notice in the back of the diaper and forming a tuft of fur at the end of it.
The fat and fluffy mutt pulls your attention to him once he makes an incredibly accurate dog whimper, squatting down with his GIANT ass presented to you but also hovering above his old diaper, blasting you with stink that seemingly isn't as bad as he made it seem... or so you would have thought until you realized you could see your nose at the end of your new muzzle. A loud thud and plop sounded from in front of you, the saint bernard man unloading a gargantuan turd that you would never have imagined could come out of something in real life, but you're suddenly taken back by a sharp, intense pain. Horns burst from your skull, and a strong, warm feeling quickly numbs out the pain entirely as your skull stops changing, your head and body now resembling more of a bull. Of course, you're still not as big as the massive dogman, but you're damn close, now. Your muscles are intense, and the strength you feel gives you a bit of confidence in this kind of situation. Of course, your balls have grown exponentially as well, and the need to breed makes your huge new cock surge upwards with lust as it all strains to remain contained in your diaper.
You look back to the dogman, his giant cheeks vibrating with every dark brown turd and dark green foggy fart that squeezes out of his donut butthole. He's sweating, panting, and you can see his own cock throbbing, the knot visible just past his incredibly thick balls, just slightly smaller than your own aching bull nuts. You can hear him explaining to you about what the special kind of beast briefs look like, but it seemed faded out or muffled as you stare longingly into his ass. Your own need to shit also arises, and painfully quick as every moment you spend holding your shit in, the more your belly grows out and fills up with more poop, presumably.