Fiolee presents: How I met your sister.

Chapter one: Meet Marceline! My evil sis!

Okay, who wants me to do a fiolee and link the kingdom of Ooo to the kingdom of Aaa?

Massive Fiolee shipper crowd: WE DO!

*sweatdrop* Okay, on to the story.

Fionna knocked on the door."Heya, baby," greeted her boyfriend, Marshall Lee, at his front porch.

Fionna blushed. Five months and you'd think she's used to him calling her "baby".

"Hiya, Marshall. Ready for our two-person sleepover?" she asked eagerly as she stepped inside his living room and set her stuff on his couch.

Marshall stared at her. Whenever it was about "just the two of them alone" moments, Fionna dressed a tad girlier than her usual self, a little more strict, and even wore outfits she would never use anywhere else. Like today, or tonight, she no longer wore her bunny ear hat, tied her hair in a long ponytail that reached her low waist, wore a black t-shirt, and knee-length green khakis.

"There's just one problem," he admitted, guiltily scratching the back of his head.

The eager blonde frowned and held her hips. "What now? Last week you said that you didn't have extra butter for the popcorn was a problem. And yesterday, you told me that a relative staying at your place was a problem." Her eyes widened in realization. "No...Don't tell me..."

He stuck his hands in his pockets and guiltily walked around the room. "Yeah. It's my sister. She's visiting for the weekend, and I don't know if you'll have any problems with her."

"Marshall Lee, we've been together for five months and you never found the decency to tell me even once that you had a sister?" she fumed crossing her arms. See? This is the strict that no one ever expected from her. Except, of course, for her boyfriend.

"I swear I tried! But she's too..." he scratched his bite marks thoughtfully. "Extreme? I don't know, but the thing is that she's here and-"

"Hey little bro!" A girl vampire said coming from the kitchen. She sported a long wool sweater dress with black and white stripes, black fish net tights, long loose black hair, and black heeled leather boots. "Ooh, is this the girl you keep rambling on about?" Marceline asked her brother, examining Fionna from head to toe.

"I guess I am," Fionna grinned at meeting Marshall's older sister. She bowed. "Fionna the human, Marshall's girlfriend."

"Marceline Abadeer, Vampire Queen, and Marshall's older sister," the vampiress returned in the same way. "You're human right? Do you by any chance happen to know Finn the Human?" she asked.

Fionna nodded. "Yes! He's my cousin," she replied.

Marceline then rolled in the air laughing. "Wow, I thought I'd never meet that goodie-two-shoes' sis! So, how's life been, my little in-law with my little brother?"

Marshall frowned. "I told you to stop calling me little! We're almost the same age, Marcy!"

Marceline just smirked. "Pffft...whatever. How old are you again, bro? Nine hundred ninety-five? Oh, oh, do I hear one thousand plus? Of course I don't. I'm the one with one thousand plus years of life. Thus, making you younger."

"So? At least I'm not daddy's little princess!" Marshall returned.

"Oh yeah?! And are YOU, mister, dad's favorite? Neither am I!" His sister spat.

Fionna sweatdropped and took her bag. "I'm gonna go unpack upstairs..."

Leaving up the stairs, tuning out the bickering siblings, the young human girl headed towards Marshall Lee's bedroom. Closing the door behind her, she addressed herself towards her assigned dresser and started unpacking clothes from her backpack into the drawers.

Lately, Fionna found herself "sleeping over" at Marshall's three times a week. So he decided to build a dresser at his room for her clothes, and the clothes she only used around him were in these drawers. And anyway, staying behind at the tree fort was lonely, because Cake and Monochromicorn have been a little...busy. And now Cake's got to take care of five kittens of her own, so yeah, nobody's at the tree house anymore, not even Beemo.

Suddenly, Fionna heard the door slam shut behind her. "Ugh, I can't believe him!" Marceline exclaimed. Seeing Fionna and their surroundings, Marceline began floating in the air.

"Oh, sorry Fionna. I just wanted to shut myself inside a random room, but instead of my guest room, I guess I wound up in my brother's crib," she apologized.

"Oh, no worries. All good. What happened out there? I came back up after the daddy's favorite bit," Fionna replied.

Marceline floated down to the floor and sighed, sitting down casually. "It's nothing. Just the normal six p. m. bickering. By the way, why are you in my brother's crib. Sleeping over for the night?"

Fionna blushed as she stuffed the last set of clothes and her backpack in the drawer. Sitting on the edge of the bed, she brushed a strand of her hair out of her face. "Y-Yeah. I was just unpacking my clothes in the dresser he made for me. I've slept over for the past couple weeks."

Marceline nodded. After two seconds of silence her lips curved into a smirk. "And by any chance," the vampiress said sitting up on the bed next to Fionna, "Have you done...it?"

Fionna frowned in confusion. "It what?"

Marceline groaned. "You know...it. How do I put it? You know...if Cake ever taught you the "tiers" of a relationship...'do not do tier fifteen' sound familiar?"

Fionna shook her head. "Yeah, I remember that explanation. But all she said was to never do tier fifteen, though she never said what it was..."

Marceline crossed her arms. Damn, this girl is hopeless. It's only luck that ever brought those two together.

"Well," Marceline said. "Have you kissed in bed?"

Fionna blushed. "No."

"Well, you should," Marceline continued, her smirk enlarging. Time to gross this girl out of her mind. "I've done that with my ex, it's...fun, I guess, when you're alone . But you're not moving in yet?"

Fionna shook her head once again. "Nope, I'm not ready for that. Someone needs to keep the treehouse's maintenance and Cake's taking care of her kittens and...I just don't feel ready to take such a big step. And plus, Cake would be devastated. You know how sensitive she is about this whole chizz? It's just luck that she lets me off the hook three nights a week!"

Marceline mentally face palmed. Damn, this girl is just as goody-two-shoes as Finn. To brainwash her into the grossest truths of a relationship is pointless. "I understand. Come on, I think Marshy-boy's cooled off by now," Marceline said floating towards the door.

Turning the doorknob, and realizing Fionna wasn't coming, she said, "So? Come on!"

That snapped her out of her thoughts. "Coming!"

As they walked down the stairs, Fionna wondered why Marshall hated his sister so much. To her, Marceline was the raddest friend ever.

So, how do you like Marcy's evil-ness? Keep following this story, 'cause it's kind of short!