I may have mentioned before that I was doing another Adventure Time Highschool AU fanfic? Well, here it is! :D I was really bored the other day and couldn't seem to write anything for any of my other fanfics. Couldn't think of one-shots either, drew a lot but was still bored. Ended up writing this. OH WELL. X3 I hope you like, I'll try my best to edit it as much as I can. Trying to be a better writer. [even though I'm not X3] Anywuz, this is gonna be about the whole highschool life of our favourite characters. SO ENJOY! :D

Marceline and Marshall had just parked they rusty old pick up truck. Marceline was first to step out,

"We're gonna have to get a new car one of these days." She grumbles as Marshall locks their ride.

"You got that right." He looks up to their school, Penward High. "Pfft. Another year of hell." He says and Marceline snickers,

"Hey, maybe being a sophomore will be better." She shrugs and they hear the bell ring,

"Oh damn. We're late." He says sarcastiacally, "Well, we better head to class."

"Yeah yeah, what do you have?"

Marshall checks his schedule, "I got... Ugh, Geometry." That sent shivers down his spine. Marceline patted his back,

"Good luck bro."

"How 'bout you?"

"Hmm... I have Logic. Whatever that is."

"We better get going."

"Yeah."

So the twins head inside, not really caring if they were late or not. They knew who would care but they just brushed it off. They had to cut them some slack, right? It was the first day.

WRONG.

As soon as Marshall stepped into his Geometry class, everybody stared at him, including the teacher. Who put his marker down and faced the 17 year old teenager.

"Well, Mr. Abadeer... So glad of you to join us."

"Yeah well..." Marshall immediately thought of an excuse, "Our car broke down and-" The teacher held a palm up indicating for him to stop.

"I don't need your excuses. Just," He gestured to the empty seat at the back, "take you seat." Marshall thought he was off the hook, "OH and," The teacher fished something out of his pocket, a pink slip. "Detention. I figured you'd do something wrong today." The class snickered and Marshall grunted as he swiped the slip from the teacher's fingers.

"Whatever..." He walked to his chair and slumped down, staring at the pink slip. "Bastard..."

As he tried to fall asleep, someone knocked on the classroom's door.

The teacher stopped talking and wondered, "Now who could that be?"

The door opened to a young girl, she looked like a freshman, "I-Is this geometry 113?" She asked,

She caught Marshall's attention, She was wearing a white bunny hat but she had blonde bangs coming out of it. She was wearing a light blue shirt with sleeves up to her elbows and a dark blue short skirt. She had high knee white socks and black shoes.

"Yes it is. Who are you?"

"I'm Fionna Catt."

"Oh! You must be a freshman. Cake's little step sister, I pressume?"

"Uhh... Yes. See, I got lost and-."

"NO, it's alright. First day and all. Come in and take a seat."

"Thanks you sir."

Marshall was fuming. 'Bastard is biased. Fucking asshole.' he screamed in his mind. He watched the girl pick out a seat, and since there was only one seat available, she sat next to him.

As she sits down he notices Marshall looking at him, "Uhh... Hi." She says. Marshall is then dropped back into reality and out of his own little world,

"Hey." he grinned.

As Marceline walked the halls slowly. she really didn't feel like going to Logic class. So she just wandered the halls then she saw something fun to do. A smirk found its way onto her lips. There in front of her was a boy, a freshman boy, obviously lost. He was wearing a white bear hat, light blue shirt, dark blue shorts, and black shoes. He had a green back pack and he was scratching the back of his head while staring at a piece of paper.

"This is gonna be fun." Marceline said to her self as she approached the lost freshman.

"-I think I just came from here?"

"Hey there."

The boy looked up from his paper and looked at Marceline, "Hey!" He grinned widely.

'A friendly type huh?' She thought to herself and smirked, "So what are you doing around wandering the halls?" She asked,

"Oh uhh... I'm lost. I can't find Biology 42." He said scratching his head again and looking at the paper. Across from them she looked through the window of a classroom. Inside was Mr. Petrikov, the teacher she dislikes the most. This just can't get any better. She grinned,

"Oh Biology 42 huh?" She pretended to look around. "Oh,well it's in that room." She pointed to Mr. Petrikov's class.

"Wow really?" He looked and smiled and turned back, "Thanks! uhh.."

"Marceline." She grinned,

"Thanks Marceline! I'm Finn! Anyway, see you later." He turned and was about to walk into the classroom.

"Whoa! Wait a minute!" She grabbed his pack and he stopped,

"What?"

"That's Mr. Petrikov."

"Who?"

"You don't know who Mr. Petrikov is?"

"Uhh, nope. Not really."

"Well the thing is, if you have a class with him it's extremely exciting." She bit her tongue to stop herself from laughing.

"Why?" Finn asked, oblivious to the prank at play.

"Well, whenever you enter the classroom late you have to do something... dynamic."

"Dynamic?"

"Yeah, that's his rule. If you're late, your entrance should be dynamic."

"How do I do that!?" Finn was now stressing out, Marceline shrugged.

"I just wanted to warn you kid. Anyway good luck!" She patted him on the head and put her arms behind her head as she walked away. '3, 2, 1.'

"wait!"

A smirk formed on Marceline's lips, "Yes?" She turned around

"Tell me what to do!"

"Hehehe, thought you'd never ask."

A few moments later Finn was wearing a purple cape, a gold breast plate and was wielding a golden sword.

"Marceline?"

"Yeah?" She was busy fixing up his straps.

"Are you sure about this?"

"Oh, definitely." She tried hard to keep herself from laughing.

"Where did you get these anyway?" Finn gestured to his costume.

"Theatre."

"OH."

"Done!" Marceline stood straight and examined her work, "You look good."

"Yeahh Uhh..." He was obviously a bit nervous, "What am I gonna do again?"

"Okay, here's what your supposed to do. You're gonna barge in there and jump onto his table and say, 'I'M FINN THE HERO! AND I HAVE ARRIVED!'." She paused to look at Finn who nodded seriously, "Then you're gonna start doing some sword action until he approves of your entrance. Got it?"

"Yeah, I think I do."

"Good."

Finn stands up straight, and cracks his neck, "Let's do this!"

"Good luck!" Marceline smiles and takes a few steps backwards. Finn backs up and huffs, he runs and charges into the room. Marceline peeks in and bursts in laughter.

"I'M FINN THE HERO! AND I HAVE ARRIVED!" The freshman screams, he starts swinging his sword around.

"WHAT IN THE WORLD ARE YOU DOING!" Mr. Petrikov screams, "GET OFF MY TABLE!"

"NEVER!"

Marceline laughs her head off, 'FINN IS SO IN CHARACTER!' She laughs so much she accidentally opens the door wide revealing her to the class, Mr. Petrikov turns to her.

"ABADEEEER!"

The whole class turns to the door and sees Marceline on the floor laughing, Finn stops his rampage and looks at the door, his face red.

"Wha-what?" He looked confused and embarrassed.

"MARCELINE!"

That stopped her from laughing. She knew that voice anywhere, "UH-OH."

She looked up and saw a pink girl standing from her seat glaring at her.

"Shit!"

"Marceline Abadeer!" She yelled,

"Well, nice seeing you Simon! See ya Bonnie!" She upped and ran away as fast as she could. She looked back and saw Finn, Bonni and Mr. Petrikov exit the classroom and see her run off.

"So uhh... You're?"

"Name's Marshall Lee."

"Nice to meet you Marshall Lee. My name's Fionna." She smiled and held out her hand. Marshall sat straight and shook it.

"So uhh... you're new here?

"Yeah I-" She feels something vibrate in her pocket, "Hold that thought." She checks her phone and her face goes slack.

"What's wrong?"

"My brother's in the principal's office."

Marshall laughs silently, and Fionna punches him in the arm. "Haha... hey! I'm sorry but... seriously? first day and he's already in the principal's office? I mean even I, 'The Delinquent' of the school, have never done that. Almost did though, once." He snickered. Fionna glared at him and read more of the text.

"Says here he was 'pranked.'"

"Pranked huh?" A grin formed on Marshall's face. "I think I know who did that." He smiled extremely proud of his twin sister.

"Hey!" The teacher called their attention. "No talking in class. I will give you a warning Fionna but Marshall Lee." He fished another pink slip from his pocket. "Another detention."

"Aw man!"

Fionna giggles, "Serves you right."

He sticks his tongue out and so does she.

This year might be even more interesting than he thought it would be.

Well what do you think so far? I'm gonna continue this no matter what cause this is mostly random stuff about highschool, no real plot or anything. Like a series and there will be times where there is some cliffhangers and plots and sad things and making up and fun friendly stuff and romance. But hey it's a progressing story that doesn't have much plot. Like Adventure Time, there are times where there is a plot and stuff. but it's mostly random, okay I'm rambling on the net. Whatever! X3

ANYWUZ! REVIEW PLEASE! :D Tell me what you think of it so far. :3