"That genie doesn't mess around," said Damon to himself in the bathroom. He had his pants down and was now seeing just how literally the genie had taken him. He didn't just have a really big dick, metaphorically horse-sized. He had an actual animal penis attached to his groin.
That was the only way to explain the dark sheath hanging off of his lower belly and the black, veiny shaft sticking out of it with the wide and slightly pointy glans. It was just like what he'd seen hanging under horses in the past. It really was way bigger than his usual instrument, but it also looked really unnatural on his human body. No matter. He still had two wishes, so it would be trivial to change back. Having one of these for a while would be an experience worth having even if it didn't help him with the ladies.
"In fact, I think I'll try it out right now," he thought.
He grabbed the top of his shaft, just under the glans, so high up above the edge of the sheath, and felt the wave of pleasure course all the way down the two-foot penis into his crotch. This was going to be great. He rubbed back and forth gently a few times and found himself leaking out a batch of precum that was bigger than his typical ejaculation. He discovered a thick ridge all the way around the middle of this monster and moaned he ran a hand over that for the first time. Soon Damon was jerking off wildly with both hands, pointing it in different directions and massaging it in various ways. More precum splattered out, and the glans swelled up and out into a really weird shape. Soon Damon's body tensed up, and he felt a surge from his groin bubbling all the way up his shaft and exploding out of his swollen glans. It was one giant wad of cum that wasn't going to be the last. He was gasping for breath as he kept launching his liquid ammo out of this cannon. He felt something twitching rhythmically at the end of his spine with every shot, but he didn't think anything of it as he was practically intoxicated with pleasure. Finally his orgasm died down and his dick was drooping down a little but, still very swollen at the tip. He looked at the chunky white puddles and ponds around him and realized that all came out of him.
"Man, that was even better than I thought it was going to be," he said out loud and lifted his limp sperm-hose with one hand as it softened and retreated a little bit more into his sheath. "Horses have it made!"
That's when he felt another twitch behind him and felt some long hairs swish sweeping across his butt. That's when he remembered the extra twitching back there that made his orgasm even better than it would have been otherwise. He realized he still didn't actually know what that was and decided to take a look. Very quickly he got a glimpse of a thick forest of long black hair starting just above his ass and dangling almost to his ankles. He experimentally twitched his new spinal muscles again and saw the whole quantity swing up and flap back down again. He understood exactly what just happened because he had seen this on horses before, too.
"Oh man, it's a tail," he mumbled, reaching down with both hands to pick it up. It was just like a horse's, and he could feel his own hands on it through all the hair. He let go and swung the tail around in big circles just to feel himself doing that. He giggled.
"I guess I'm going to have to be careful that I don't turn all the way into a horse," he thought. It made sense that magically giving himself a horse cock might inadvertently turn him into a horse, even though he knew he didn't wish for that. He wasn't worried, though. After all, he still had two wishes, and using his new dick once had only given him one extra horse part. He figured he could still get some mileage out of this first wish before it was time to set things back to normal.
"Are you okay in there, Master?" asked the genie from outside. "I must warn you that your wish for a partial transformation may have side effects."
"So I've noticed," answered Damon from the other side of the door. "Don't worry, everything's fine. I'm getting dressed again and I'll be back out soon."