Tentacle Donnie
It was late at night at the farm house. April and the turtles have settled in for the night couple hours ago, but Donatello remained restless. He just couldn't find the slumber he was looking for, like normal. So he decided to kill some time and find something to do in his temporary new lab.
He threw the covers off his legs and hopped out of the bed. He thought about leaving his gear behind but he decided against it for safety measures. I picked up the white strips of cloth and began to wrap them around his green fingers and feet. After he was done with the cloth strips he picked up his right knee pad and slipped it on. Before he picked up the next one he heard a strange sound come from outside. Forgetting about the rest of his protective pads or belt he grabbed his mask and tied it over his eyes on his way down stairs.
He slowly opened the door and out to the pitch black world of darkness. He heard the sound again, so what ever was making it, wasn't gone. It sounds like a slimy slither. Like something wet sliding through grass.
He stepped outside, unaware of what could be lurking and watching him in the dark.
"Hello?" Donatello called out. He heard the sound again.
"Who's there?" He asked. The sound got louder....and closer.
"Show yourself!" He yelled out. Nothing was heard. After a few more seconds he thought he scared it off. He looked over to the barn that held his lab. He took a few more steps towards the barn, that is until he felt something wrap around his leg. He snapped his head down to see a pink tentacle. It pulled on his leg, knocked him onto his carapace, and started dragging him further away from the farm house. He tried screaming for help but the thing dragged him too far away for anyone to hear him. 
The tentacle stopped dragging him and wrapped itself  further up Donatello's right leg. He tried kicking at it to free himself when another one came and wrapped up Donnie's left leg. The tentacles then tightened their grips and pulled his legs apart, Donnie then realized what this creature was trying to do: rape him. He felt more of the slimy things wrap around his arms. One of them managed to find his tail. Donnie tried to keep it closed but a wave of tired hit him. The tentacle pushed through his tail, its own slime becoming lube and started thrusting in and out of Don's tail. He whimpered from the pain that shot through him every time it thrusted back into him. 
He felt another slimy tentacle crawl up to his face. It came up to his mask and removed it from his eyes to his neck. He felt something travel down his plastron to his closed slit. He didn't want to be claimed by this creature. But he was so tired from not sleeping. The tentacle began pushing and rubbing against the barriers to get to his cock. 
Another tentacle found his entrance and pushed through the tight ring of muscle, not even preping or waiting for him to adjust it thrusted in and out much like this thing was doing to his stinging tail. The tentacle at his slit finally  pushed through the walls and wrapped around his not so hidden cock. He cried in pain out as he was forced to drop down. When he dropped down the tentacle began to pump and some how lick Donnie's cock. And with each pump, the thing in his entrance would strike his prostate, sending waves of pleasure through him. With this being his first time he reached his climax very quickly. The tentacle traveled to the head of Donnie's cock and suck or drank any cum that shot out. This creature wasn't satisfied with one helping of cum. It began to pump and thrust the tentacles into him harder and faster. He churred in pain and pleasure, the pain from his tail and the pleasure from his entrance and cock. The tentacle on his cock squeezed through the head, sitting inside and waited for a second helping of hot cum to shoot out.
He cried out as the tentacle in his tail stopped thrusting, but traveled in deeper, hurting Don on purpose. It was a threat, meaning if this thing didn't get more sweet hot come, someone is getting hurt. Donnie managed to reach the edge again and feed the creature having its way with him.
The monster had a go with him five times in total before it was finally finished. Every time Donnie took too long either the tentacle in his tail or entrance would push in deeper, causing him extreme pain and for tears to escape his eyes, only for the monster to lick them up. He felt the slimy tentacle things unwrap around his cock, tail and entrance and fade into the forest. Slime mixed with a little left over cum from his cock mixed with a good bit of blood dripped from his entrance. Donnie was so exhausted that he passed out right there. Unaware that the creature could come back for more in his sleep.