Weregoo
Felis was sound asleep in his bed when a meteor the size of a baseball went through his window. The ball of rock fell surprisingly quiet on his carpeted floor. When it finished rolling, it made a hissing noise and fell apart in halves. Inside was a goo like substance. If one were to look at it, it would blend in with the darkness with its pure black color. The goo started to wiggle to life and started to sense around for a host for it to live in. Almost immediately, it senses poor, defenseless Felis and start to crawl in his direction.
***
Felis had just gotten into puberty. His friend had been supplying him with 'research material' to help him get rid of the constant boners he had been getting. In fact, he was dreaming of one of these fine ladies right now. His young cock throbbed against his blankets as he imagined himself having his way with her. Then he felt something pressing against his butt cheeks. To the goo's delight, he seemed to ignore it. It spread his virgin hole and pushed itself inside. The extra stimulation caused Felis to moan aloud and grab his rock hard cock. After the goo slid all the way inside the boy it raced toward his prostate and wrapped itself around the area. The poor boy didn't know what hit him and caused him to have the biggest orgasm he ever had. Cum flew out of his cock, coating his lower body and sheets in his seed. Little did he know, the slug made him expel all of his human semen. After all the commotion, Felis began to think of older, jock high school boys. All the while, smiling not thinking of his drastically changed sexual orientation.
***
Felis woke up around mid-day. Outside the sun was shining and looked like a beautiful day. As he got out of bed, his body felt sticky. He went into the bathroom to clean himself up. After drying off and getting dressed, he headed downstairs. When he went into the kitchen he saw his parents all dressed up. "Going somewhere?"
His mother looked at him, "About time you got up. Your father and I are going out to a long business dinner."
"So I will be by myself?" he asked hopeful.
His mother laughed, "No, I am having Chad next door watch you while we are gone."
As if on cue, the 16 year old basketball player walked in wearing his uniform under his coat. "Hey, little man."
"Hugh, we better get going. Behave yourself." With a kiss on the head, both his parents walked out the door and left for the rest of the night.
"I'm going to be in the living room watching TV if you need me," he said taking his coat off revealing the high school's mascot, a panther.
Felis felt his dick stir in his pants and continued to stare at Chad's jersey. When he moved into the living room, he snapped out of the trance he was in. A little confused he went back to his room to play some WoW. He played for a while and lost track of time, not noticing the sun beginning to set behind the houses. When he logged off, he saw the last rays of sunlight disappear. At that moment the alien slug inside him started to act up and rubbed against his sensitive prostate. He doubled over as the sudden pleasure hit his body hard. His cock became instantly erect and started to leak pre into his clean shorts. It didn't take long for him to take his pants off. He had had an erection before, but this felt different, more demanding than the others. He began to feel hot everywhere and took off his shirt too. Another wave hit him and sent him to his knees. He moaned loudly as he asked, "Why am I so horny?"
Outside his door, Chad came up to check on his charge. When he heard Felis begin to moan in pleasure his pants began to tent outward. He cracked the door open to see what was going on in the room. Inside he saw Felis on his back jacking off his young cock. By the look on his face, he was in pure bliss. He couldn't help himself and he reached into his shorts to relieve his straining hard. Chad had had a crush on Felis ever since he moved in last year. The more time time he spent with him, the more he wanted to hug him and kiss his lips deeply. Then an idea came to his mind. He walked into the room quietly and snuck up on the moaning boy on the floor. Chad got on his knees and pushed Felis' hands away from his cock. Almost immediately he took it into his mouth and started to suck it while fondling his balls.
"Ch-Chad?! What are you doing here?"
Chad did not reply, he kept on going and hit a pleasure spot and caused Felis to buck into his face. Chad took advantage of his weakness and flipped Felis around, his firm ass staring him in the face. He then proceded to lube his virgin hole by licking it. When he had finished lubing him up, he began probing Felis' tight hole. Without any warning, he thrusted his throbbing cock all the way into Felis. Right at that moment, Felis' older brother Mark walked in on them.
The air smelled thick with the musk of the two boys making out in his brother's bedroom. Unbeknown to him, a strong pheramone was being emitted from the alien creature inside of Felis, making Felis sexually irresitable. Mark looked down to see his instant boner poking out the top of his tight shorts. When he removed his pants, his cock stood straight out. He had never been the one to have a lot of sexual urges like most boys his age, this is one of the few times he actually got an erection from something. Then, like a voice whispering in his head, he had the idea to out his cock in his brother's mouth. He walked slowly over to his brother's face, his body rocking from Chad's thrusting. Felis looked up at his older brother with pleading eyes, as if he had read his mind. He placed his cock on Felis' face and Felis took the hint and took it into his mouth slowly.
Felis' young mind exploded with pleasure as he was being pleasured from both front and behind. The additional stimulus made the alien entity more nutrients to where it melded into his flesh. As the orgy went on, it made its way to Felis' balls and assimilated itself to his sperm. The additional mass made the boy's balls grow one half times its original size. He felt Chad beginning to pick up the pace of his thrusting, signaling that he was close to releasing his load. Felis clenched his ass to tease his neighbor, but the teasing went too far as he felt Chad's warm cum begin to fill him. Chad's orgasm went on for a few moments, some of his cum escaping out of Felis' anus.
In all the excitment, Felis could not hold his own back and cummed all over his floor. His orgasm caused his lips to tighten on his brother's cock, making him shoot in his mouth. Both Chad and Mark fell on their backs breathing heavily. Felis too was exhaisted and laid on the cum covered floor. Felis looked down for a moment to see that his cum was oddly colored, it was black. He lifted his hand up to take a better look at the gooey stubstance. He was startled to see it begin to crawl up his arm, not only from his hand, but the floor as well. Felis began to panic as it engulfed his entire hand and arm, making it look like a front leg of a black panther.
Chad and Mark saw the change to Felis' arm and got spooked. The both bolted toward the door leaving poor Felis to his fate. The black cum began to engulf his entire body, going into any opening; mouth, ass, and even his penial hole. Felis' cock became erect again. The goo climbed all over his body, making it feel like a body suit. But this body suit began to take on the form of a panther. It was so alive that the tail even flicked back and forth like a real panther. His feet fit into boot-like digitigrade paws, the goo that was on his face pushed out like a muzzle, but the most peculiar thing that changed was his penis. The goo on his penis actually changed into a blood-red color, making a feline condom spikes and all. When the goo was finished with its job, it left a realistic looking rubber horny panther.
The new panther smelled the air, looking for a new mate. He caught the scents of both his brother and Chad from the cum residue in his room. The panther Felis walked out if his room, ready to stalk his new prey.