Not owned by me. By Deckofdragons
It's not plagiarism if you give credit
Copied from https://archiveofourown.org/works/15019862/chapters/34844693?view_adult=true
The rattling against the door increased as whatever was inside started pushing against it with renewed vigor. Until it was high enough for a large white... paw(?) to stick out from underneath it, followed by another as whatever it was struggled to fit under the gap. They made wet plopping sounds and looked to belong to an ooze monster other than for the vague shape of a dog paw.
Whatever it was though did not bode well for Sans. Tears of fear came to his eyes as the door kept rising and more of the thing was visible until it managed to get its head and shoulders in. The rest of it quickly followed and Sans screamed at the sight of its face, or lack thereof. Underneath its decidedly pointed dog ears was a gaping black hole that pulsated as it howled in triumph.
Its tail wagged hard enough that its entire goopy body shook as it bounded over to Sans. Sans screamed again as it loomed over him, thrashing against his bindings. It was huge, more than twice his size. It could eat him if it wanted to.
It jutted its head between his legs, putting its 'face' inches away from his pussy as if sniffing it. Its tail started wagging even harder. It sniffed up his body, pausing at his face. It growled, wet and horrible it sounded like it came from a demon dog whose domain was the darkest depths of the ocean.
Whimpering, Sans clenched his eyes shut, forcing out more tears. A thick wet substance dripped down onto his face, was it drooling? He didn't dare open his yes to find out, he didn't want to know anyway.
Something gripped onto his muzzle and tugged up. He yelped as eyes fell open to see that wet goopy tendrils had emerged from the impenetrable blackness of its face. He thrashed his head from side to side as it kept tugging on the muzzle as if trying to get it off. Why would it want that?
"No, bad dog, leave that on." Gaster's voice was muffled by the intervening glass but unmistakable. "I don't want to listen to him whine and complain."
The 'dog' ignored him though and kept tugging at the muzzle, pulling Sans' head up with it. It growled again as it kept tugging. Eventually its tendril things snaked down and pulled on the straps themselves, hard enough to make them stretch and after a few minutes filled with Gaster trying to get the 'dog' to leave the muzzle alone they snapped.
"Please don't hurt me," Sans whimpered as the dog tossed the metal bit off to the side. It made a loud clank wherever it landed. Sans didn't look though, his eyes were locked onto the gaping maw of the demon dog above him as its tendrils snaked back into its face... for now. The table was positioned at the perfect height for it to loom over him and was the perfect width for it to not get in its way. "Have mercy please." Could it even understand him? If so, would it listen?
Its paws made heavy wet plopping sounds on the floor as it shifted its position over him, straddling him. It whined excitedly as it stilled. Surely it wouldn't really rape him, right? It was a demon goo dog, what would a demon goo dog gain from sex with a skeleton monster? And it was so big, it could break him and would definitely hurt.
Something grew out of its body and pushed against Sans' clit, something thick and disgustedly soft, like how he would imagine rotting flesh would feel like. Sans fought against his bindings and tried in vain to dispel his pussy but it was no use.
"Please no, please no, please no, please..." He cut off with a scream as it thrust in. It was huge and its soft gooeyness meant it pressed perfectly against every inch of his sensitive inner walls, filling him completely. His body convulsed with an orgasm from that alone, clamping even tighter around its dick inside him. He sobbed and panted his way through it as the demon goo dog let out a wretched wet bark before pulling roughly back and slammed into him again, pulling yet another scream out of him.
