"Good morning, babe." Mary told her boyfriend as she woke up. It's still pretty dark so she didn't noticed something odd with Dave until he woke up.
When he opened his eyes and tried to say a word, nothing came up except for a loud neigh that made him to realize he can't talk anymore. Desperately he tried to stand up, and realized that his body felt numb and quite different.
Mary was fully awake now and she immediately noticed that Dave was now a full black shire horse. His long equine back was next to her while he desperately tried to stand up using his new hooves.
"Dave, calm down." Mary said as she inspected her boyfriend's body. He wasn't like her. He looked like a regular horse, the ones you can see in a barn or in horse races. "The vial effect is temporary. You'll be back to normal. I promise."
"When?! I don't want to be a fucking horse!! My parents are coming to visit me today!!!" Dave was yelling as crazy in his mind but all that Mary could hear were loud neighs coming from a freaked out animal.
"I know you're scared, but we can't do much right now. Come on, let me help you to stand up. It must be difficult to get used to a new anatomy." Mary carefully guided Dave to move his fore legs and then his back ones until he was up... Well, in his four stance.
When Dave stood up Mary noticed that his new equine shaft was hanging freely from his sheath. She had felt it growing up inside her last night but it another thing to look at it. It was long thick mottled and totally different from his former human shape. The medial ring and flat tip gave it a feral look that was starting to arouse her.
"You won't mind if I do this, won't you?" Mary said as she kneeled and started to suck Dave's horse cock. At first, he wasn't in a mood for this, but who can say no to a good morning blowjob? Especially when you have more meat to get pleasure.
As Mary moved her mouth in and out of Dave's shaft trying to put in as much meat as she can. Dave's new horse balls wete slamming her chin and Dave's flanks. That's how he realized how hefty he was now. He was full of fresh manmilk ready to come out or maybe he should say horsemilk.
That's when he remembered. "I'm a horse! My parents will come in my house at any moment! I need to do something!!" He was getting to his climax but he moved before Mary could suck his cum. Instead he shot his big gooey yellowish seed in the ground. It smells awful but it was the least if his problems.
"Sorry, babe. I needed to do it." Mary said as she stood up licking her lips with her big tongue. "I'll help you now, but first, I need to go to the bathroom."
Dave sighed in his mind, he was doubting he will be back to human in time. And as he thought he felt something moving in his bowels. "Are horse bowels like human ones?" He didn't want to think to much about it but he also didn't want to shit in his girlfriend's room.
While he thought about it he felt something wet between his... hooves? He looked down and noticed a strong and thick stream of piss coming out of his long horse dick. In that moment, he was understanding the meaning of pissing like a racehorse. "Oh lord! I didn't even realize I needed to piss." He was kinda ashamed. "Well, at least I'm not..."
"Hey, honey. I'm rea-" Mary was coming in when she noticed horrified the horse that was her boyfriend shitting a big amount of horseshit in her floor.
"Oh, honey! Oh, honey! Oh, honey!" Dave felt so ashamed and if he could blush he would be totally red right now. "I'm so sorry! I didn't want to! My... my ass moved by its own!"
"I guess I deserve this for turning you into a horse." Mary sighed. "Well, I'll clean later. Now I'll look for a way to turn you back to normal. I remember your parents are coming and you are not the stud they're expecting to see."