A/N: Hey, this is my first Adventure Time Fiolee fanfic hope you like it!

Disclaimer: I do NOT own Adventure Time OR the song 'Scotty doesn't know'

Fionna, the blonde Adventurer sighed as she looked out the window. It was a warm cloudy day weird enough and she was stuck indoors with her boyfriend Prince Gumball. They were the only ones there since Cake was out with Lord M. For some stupid reason he had no desire to be outside he'd rather sit and drink tea in case it might rain. Not cool. "So, PG wanna play Bemo?" Fionna asked wanting to do something.

"No, why don't we watch a movie?" PG asked and for the first time in the whole day it sounded interesting.

"Sure, what do you wanna watch?" Fionna asked and PG smiled.

"I have the perfect movie. Just give me a second." PG exclaimed and went to our movie rack before taking a movie out and placing it in the tray. Before, she knew it sh heard the music to the show'Cupcake Wars'. Fionna almost groaned the title sounded cool until you realized it was just a baking contest. She slumped down on the couch away from PG and watched. Until the blonde hatched an idea even though it was kinda mean she had to do it or watch 'Cupcake Wars' again. Fionna started coughing a whole lot and soon was in a coughing fit. "Fionna! Are you okay?!" PG asked placing a hand on her back.

"I don't think so. I haven't been feeling well lately. Maybe, you should go I wouldn't want you to get sick before your party this Friday." The girl stated trying not to smile as she saw that it worked.

"Okay, I hope you feel better Fionna. I'll try to stop by tomorrow." PG stated and left quickly obviously not wanting to catch anything. Finally, deciding he was a good distance by now she got up and grabbed her Adventurer backpack and set off to a very important person's cave. Once there she walked in the cave she smiled hearing a low bass coming from the house. Walking in the living room she saw Marshel Lee jamming out on his axe.

"Hey, Marshel." Fionna said plopping down on the couch. Marshel Lee stopped and put his axe down before floating over to her a smirk on his face.

"Hey, babe." Fionna blushed at the nickname and before she could say anything she was pinned to the couch and cold soft lips were pressed to hers. She reveled in the familiar taste of him and wrapped her arms around his neck kissing back. Yep, as much as she didn't exactly want to believe it she was head over heels in love with the hot vamp and they'd been going out secretly. It was just the excitement of a secret love affair. Though she could see this going further than just an affair and that was the problem. When breaking the kiss their foreheads were pressed against each others. "I thought you had to spend the day with Prince Gumwad." Marshel said.

"I managed to get out of it." Fionna answered smiling. He smirked and said cockily.

"Aww, you missed me." Fionna playfully rolled her eyes. "You know Prince Gumwad asked me to be the entertainment at the party this Friday." He said and Fionna raised an eyebrow at this.

"Really? Huh, cool beans. What are you going to play?" Fionna asked. A devious smile crept on his face.

"Something." Then before Fionna could ask he began kissing her again. Unknowing to her a plan was forming in his head.

*Friday at the party*

Marshel smirked evilly almost as he walked up to the stage he was going to perform on. Once on he got everything ready he started the music and yelled. "Hey!" To get everyone looking at him and he started ready to put his plan into action.

"PG doesn't know,
That Fionna and me,
Do it in my cave every Sunday."

The look on everyone's faces were pricless! Exspecially Prince Gumball's! Marshel was enjoying this and smirked his fangs showing.

"She tells him she's out fighting,
But she doesn't go,
Still shes on her knees, and...

PG doesn't know, oh.
PG doesn't know-oh.
So don't tell PG!
PG doesn't know,
PG doesn't know.
SO DON'T TELL PG!"

He began floating around getting into the music. Fionna's face was a bright red and the Prince's face was dibelieving and angry. Everyone started dancing listening to the music laughing.

"Fionna says she's out shopping,
But she's under me and I'm not stopping.

Cause PG doesn't know,
PG doesn't know,
PG doesn't know,
PG doesn't know.
So don't tell PG.
PG doesn't knoooooow...
DON'T TELL PG!"

Marshel Lee walked off stage and smirked straight at the Prince in a taunting way as he sang. He went invisiable and worked his way to behind Fionna and sang his next words becoming visable to everyone.

"I can't believe he's so trusting,
While I'm right behind you thrusting.

Fionna's got him on the phone,
and she's trying not to moan.
It's a three way call,
and he knows nothing.
NOTHING!"

He wrapped an arm around Fionna's waist and pecked her cheek before floating away.

"PG doesn't know,
PG doesn't know,
PG doesn't know,
Don't tell PG.
Cause PG doesn't know,
PG doesn't knoooooow...
SO DON'T TELL PG!

We'll put on a show, everyone will go.
PG doesn't know,
PG doesn't know,
PG doesn't knoooooow..."

He shrugged when singing the next lines and grinned almost like he was laughing at Gumball.

"The parking lot, why not?
It's so cool when you're on top.
His front lawn, in the snow.
Laughing so hard, cuz...

PG doesn't know,
PG doesn't know."

Marshel did a quick guitar solo type thing and then uttered his next line nodding and smiling smugly making Gumball's mouth drop and look at Fionna who blushed a terrible red color.

"I did her on his birthday."

"PG doesn't know,
PG doesn't know,
PG doesn't know,
PG doesn't know,
Don't tell PG.
PG doesn't knoooooow...

PG will know,
PG has to know,
PG gotta know,
Gonna tell PG,
Gonna tell him myself.

PG has to know,
PG has to know,
PG has to,
PG has to,
PG has to go!"

By the end he started fist pumping as the crowd sang with him.

"PG doesn't know,
(Don't tell PG)
PG doesn't know,
(Don't tell PG)
PG doesn't know...
PG's gotta go!"

When the song ended PG turned and looked to Fionna. "Fionna, is this true?!" He asked his cheeks red with anger. Thoguh before she could answer Marshel wrapped his arms around his lover's waist and smirked saying.

"You better believe it is blow pop."

"Marshel..." Fionna said trailing off because deep down she had wanted to tell him something like that since they started dating. Obvious that it was over between Fionna and Gumball he practically stomped away. But as Marshel turned her around a kissed her passionately she couldn't find it in herself to care even when Cake came over and freaked out.

A/N: Hey hope you liked and sorry if it didn't make sense or their OOC! Thank you for reading please R&R!