Chapter 1: how are babies made?

"Hey, Marsh, guess what Cake told me earlier," Fionna spoke, leaning her head on his thighs while the rest of her body took up his red couch.
"What?" He asked flicking one of her bunny ears.
"Don't just say 'what', make a guess," she said sticking out her tongue.
"Uh, Mochro got knew horse shoes," he guessed randomly.
"Nope."
"Cake baked a cake and question the morals of eating it."
"Nope."
"She accidentally swallowed another hair ball."
"Nu-uh."
"Uh, she went on a crazy adventure."
"Dude, it's not about Cake," she informed him.
"Just tell me what it is then," he replied, seeming as bored as she was impatient. She sighed.
"This morning, Cake told me that Mrs. Pig is preggers," she told him.
"Again?" He asked now picking at his nails. The black Polish he was dared to put on by Fi a week ago was finally starting to chip.
"Yeah."
"Which one is this one? Her fourth?" He questioned looking down at her face.
"Fifth," she said.
"Damn! Tree Trunks needs to calm down," Marshall joked with a brief laugh.
"Huh?"
"He needs to pull back on the reins, chill out for a while. Those two are like rabbits," he continued.
"Rabbits?" She questioned, tilting her head in confusion.
"Yeah…because rabbits bang a lot," he explained for her.
"'Bang'?"
"Y'know, sex," he said and returned to his nail.
"Marsh, you're confusing me," she told him.
"With what?" He asked, his tone on the impatient side.
"What does Tree Trunks and rabbits have to do with Mrs. Pig being prego?" She questioned. He looked down at her for a solid thirty seconds before bursting out laughing. Fionna glared at him as he chortled and snorted in his naturally heinous laughter. "Marsh, I'm serious." His laughter finally subsided and he patted her head.
"Nice one, buns, but your 17. There's no way you can convince me you dunno about the birds and the bees anymore," he said with a smug smile.
"Marsh! You're seriously confusing the heckyy outta me right now! What does Mrs. Pig being pregnant have to do with birds and bees and rabbits and Tree Trucks?" She snapped. He was silent. Shit, she really didn't know…Fionna sat up and turned herself to look at him.
"Marshall…how exactly are babies made?" She asked him.
His eyes instantly widened at the question and he ever so slightly blushed. He was so not ready for that question, and he especially was not about to explain to Fi the magic of making love. Mostly because he might mess up and accidentally imply that they start doing the lovers tango on his fucking couch. Except it wouldn't be the couch fucking…Anyways, a one thousand year old with the mentality of eighteen was not the best to explain that shit.
"Do you really not know?" He was hoping she was just pulling a great big prank on him so he would look like a fool being all flustered about explaining sex.
"No, do you really think Cake would tell me about it ever?" Alas, he was wrong.
"Uh, maybe you can ask again?" He suggested, feeling a little nervous now.
"Ugh, she'll just say I'm too young still, and you said I should know this," she replied.
"I did?" She nodded, and Marshall sighed. "Look, Fi, I'm not the best to explain this sorta thing to you…"
"Why not?" She challenged folding her arms.
"Because I'm your friend and it would be awkward," he told her, starting to get defensive too.
"How would it be awkward?"
"It always is, and it's usually with your parents and I'm not your dad," he retorted.
"Ugh, you're the only person who can explain it to me, and if you can't I'm just going to have to find out myself-"
"No! Don't do that!" He hissed. She frowned.
"Is it really that bad? Just tell me already," she nagged. He sighed.
"Fine…I'll tell you, but I'm only telling you. This isn't going to be around of fucking show n' tell, got it?"
"Huh? What does that mean? 'Show and tell'?" She asked. He groaned and slapped his palm over his face.
"I mean, if you're curious to what something looks like I'm not gonna show you how to do it," he explained.
"Oh…why not?" Marshall turned beat red.
"Do you want to get pregnant or something?" He nearly shouted.
"I wasn't asking you to do it to me! Just…show me like 5 feet away," she muttered the last part shyly. He sighed for the third time; this girl is a handful.
"Maybe. We'll see. Anyways, what do you already know about pregnancy?"
"Uh…that's when the baby is in the mothers stomach," she said.
"That's it?" She nodded. "Okay, you're already wrong so let's start with the parts."
"What parts?"
"I'm about to explain that, dumbo," he snarked. She rolled her eyes.
"Explain faster," she nagged.
"Whatever. You know what makes a man a man and a woman a woman when they're born, right?" He asked. She nodded and grinned. "Tell me."
"Well, guys have something called a peanut and girls have boobs." Marshall couldn't decide if he should laugh or cry. This was ridiculous. Cake needs to educate her sister!
"No…no, that's…that's just really wrong," he told her, her face dropping instantly.
"What? That's what Cake told me."
"Sweetheart, you misheard her. Guys have penises, and girls don't just have boobs. They have vaginas." Her brows furrowed.
"I…don't know what those are," she admitted.
"Of course you don't, but that's okay. You…" he placed his hand on her shoulder, "have a vagina." He informed her.
"Really? Where?" She asked. Marshall clenched his jaw, and waved his hand in the direction of her crotch. She looked down. "Oh, well I can never see it because it's always covered in a lot of hair." He grimaced, 100% certain that she would not want him to know that if she really understood.
"Okay, that's called pubic hair, and-"
"Do you have that too?" She interrupted. This was just getting more and more awkward for Marshall, yet it seemed like nothing to her. He blushed.
"Y-yeah, all people do unless they decide to shave it off or something."
"Do you shave it?"
"I just told you I have pubs, of course I don't shave it," he snarked.
"Oh, yeah. Do I have to shave it?"
"No, it's more of a personal preference."
"Okay, and you have a pe-nis?" She asked.
"Yes. Most men do," he replied.
"What does yours look like? Is it in the same place?" She asked innocently and glanced down at the crotch of his jeans.
"Y-yes, and I told you I'm not gonna show you things," he reminded her, getting redder.
"Then draw a picture."
"Fi, I sing and I play instruments, but I don't draw."
"Then show it to me," she ordered, becoming as frustrated as he was embarrassed.
"I said I'm not gonna show-"
"Fine, I guess I'm just gonna have to got out there and find out for mysel-"
"Glob! You're fucking impossible," he growled standing on his knees and undoing his belt. She giggled and watched as he undid his pants and pulled them down slightly. "A-and if anything happens it's you're fault," he grumbled.
"How is it my fault? I don't know what would be happening if anything happened," she responded.
"It's your fault, now shut up," he hissed and slipped his finger under the elastic of his boxers. He sighed. "Okay, no…touching, or pointing, and especially no laughing," he instructed. She nodded and he braced himself for the response as he tugged down the elastic.

Heyo. Quick chapter but right now I'm functioning on five hours of sleep. Hope you like it, and there will definitely be a second chapter! ^_^