***Takes place the night before the battle with Lucifer in the episode "Abandon All Hope". I wanted Jo and Dean to hook up already... but it didn't happen. So, here's my take on what would've happened if Jo gave in to Dean's antics.
It might've been the night before the end of it all, but the Harvelles, the Winchesters, Bobby, and even Castiel wanted to go out with a bang. Castiel was doing shots, to Ellen's amusement, while Bobby, Dean, and Sam were talking strategy. Deans eyes soon began to wander and he saw Jo in the kitchen. If this really is my last night on earth, he thought, I might as well try. Her blue jeans were cupping her in all the right places while she was bending over the fridge, Damn, Dean thought, What a nice ass. He came up behind her whilst drinking his beer. She turned around, her blonde hair bouncing, and narrowly missed hitting his chest. Jo could practically smell his testosterone.
"So... dangerous mission tomorrow. Guess it's time to eat, drink, and, you know, make merry," He lightly chuckled, trying not to give away his unwholesome intent.
Jo arched her eyebrows, "Are you giving me the last night on Earth speech?" She smiled, flattered but skeptical.
"What?" He covered for himself.
"What?" Jo played along.
He knew he'd been caught hitting on her, but he wouldn't let her slip by that easily, "No... If I was, would that work?" Dean inquired.
Will it? Jo thought, I've wanted this for a while now... dammit. I should take the offer already. No, no. Self-respect. She looked into Dean's eyes, and she knew she was a goner. His eyes were beautiful; they were layers of different emotions all at once. Humorous, playful, miserable, angry, full of desire. Those eyes made her melt. Goodbye self-respect, she thought, I want this, he wants this. We're adults.
She bit her lip seductively, "It just might."
Dean was thrown off guard, That actually worked? On Joanna Beth Harvelle? Hell, I'll take it. Jo was already kissing his lips. His hands went through her hair, wrapped around her waist, and rested at the small of her back.
"Where should we go?" Jo asked, breaking their kiss, "We'd have an audience here."
"Follow me," he said.
Within seconds, he was leading her outside of the house. Jo held his rough hand and let him lead her down the porch steps. Dean quickly opened the door to the Impala, and let go of her hand to make a little room in the back.
"Car sex?" She asked.
"You don't like it?"
"Never had it. But, like you said, it's time to make merry. Let's do it," Jo pulled his face down to meet hers, and their lips started to devour each other.
Dean pushed her lightly onto the seat of the car, and closed the door behind him. Clothes were being ripped off, and hands were wandering. He nibbled at her ear, and then started to work on a hickey for her neck. Panting, Jo ground her hips against his while she kissed his shoulder.
"Oh, Dean," She whispered.
His groin hardened considerably at her aroused whisper, and he knew he had to have her, right then and there. Jo took off her shirt; ready to bare it all, so Dean freed her perfect breasts from their shell, and began to trace his fingers over them as they rose up at his touch. With another swift movement, he removed his shirt, and Jo helped his with his pants. Soon, they were both naked, and they took a moment to look at each other. Hastily, Dean began rubbing his erection on the inside of her silky thigh.
She moaned in blissful anguish. Her folds were growing wetter every second he was teasing her. Jo could feel him throbbing, and aching, to be inside of her. She wanted to take control.
"No more games," Jo said breathily, and flipped herself on top of him.
She parted her legs and let his length enter her. Jo took a moment to adjust and mount her steed, and she could see the hunger in Dean's eyes. She started riding, pumping herself on it slowly, and started to thrust her hips at a medium pace.
Oh, yes. What a view. Dean saw both breasts quiver with every thrust she made.
They pounded against one another in a hot, wet mess. Building up to their orgasms Jo began to ride his member faster, and stimulated herself even more. She could feel it building up inside her, and by the grunts Dean was making, he was almost there as well. Dean came first, with a mix between a growl and a groan. Jo followed; she peaked after her final thrust. Their bodies spasmed for a couple seconds in release, and then they both fell silent.
Dean and Jo breathed heavily, then grabbed their clothes that had been left carelessly on the floor of the car.
"That was... fun," Dean said satisfactorily.
"Look," Jo scoffed, "We've clouded up the windows."
Dean looked and saw that all the Impala's windows were steamed up pretty good. He used his pointer finger to press against a window. Jo wondered what he was doing, then saw him making a shape. He had formed a heart in the foggy glass.
"Well, well, well. Aren't you romantic?" Jo laughed and playfully pushed one of his strong arms.
"Well, it is our last night on earth," Dean said sarcastically with a smile.
"I'm sure it is," Jo rolled her brown eyes and laughed.