Awkward Colouration and Sexual Frustration

"Marshall, ow! Stop it," Fionna said, shoving him hard in the chest. He soared backwards, stopping only when he hit the wall of his living room. Fionna frowned, rubbing her neck as she set down her game controller."What the math, dude?" she asked. "I mean, I know you're a vampire and all, but really? I thought we were friends."
Marshall floated upwards, his head brushing the ceiling. "We are friends," he said, looking hurt. "I just-"
"Just what?" Fionna asked harshly. "Just had a sudden desire to drink my blood?"
Marshall scratched the back of his head, slowly moving towards the ground.
"Something like that, yeah," he said. He smiled wryly. "So much for shades of red, huh?"
Fionna rolled her eyes. "Marshall Lee, you are the only guy I know who could possibly make a joke after attempting to eat someone."
Marshall sighed, swiftly vaulting over the arm of the couch Fionna was sitting on, dropping lazily onto the cushion next to her.
"I wasn't going to eat you," he explained. "I didn't even mean to bite you. I'm sorry, okay?"
She grunted, crossing her arms.
"Hey," He pulled at her chin, forcing her to look at him. "I'm sorry." She scowled at him for a moment, but he flashed her one of his signature grins and she smiled.
"Fine," she said, punching his shoulder lightly. "But try that again, and you'll end up doubly-undead, got it? You green freak." She shook her head, turning back to the screen. "Aw, now look what you did," she said, and he groaned as he realised that both of their players had died.
"I guess we'll have to start over," Fionna said, picking up her controller from the ground. Marshall scooped his up from where it was wedged between the couch cushions and grinned.
"I guess. But this time, I'm gonna beat you for sure, tomboy," he said, elbowing her in the ribs. Fionna stuck her tongue out at him.
"You're on, vampire," she replied, elbowing him right back, but twice as hard. Not about to be beaten by a girl, Marshall quickly responded by shoving her in the shoulder, which caused Fionna to shove him back, which set off a chain of pushing, shoving, and rabbit-ear pulling, eventually ending up with both of them on the ground, Fionna (now hatless)having pinned Marshall down by the shoulders.
"I win again!" she cried out triumphantly, throwing her arms above her head.
"Not a smart move," Marshall growled, rolling over so that he was sitting on top of her hips. "Pwned," he said, leaning down and exhaling lightly through his nose.
Fionna wrinkled her nose, sticking her tongue out again. Unfortunately, Marshall had chosen that exact moment to stick his tongue out at her, and...
"Gross!" he shouted, zooming back to the wall and wiping his mouth on his sleeve. Fionna had scrambled backwards, making odd faces and noises that sounded remarkably like Cake hissing, until they were on opposite sides of the room.
"That was-" they said simultaneously. They both laughed nervously, Fionna biting her lip and Marshall avoiding her gaze.
"Um," he said, shifting uncomfortably.
"Yeah, that- that was... Sorry," Fionna said awkwardly.
"It wasn't your fault," Marshall said, sliding down the wall to sit on the floor. "But, uh-"
"Yeah?" Fionna said, glancing up at him. Marshall scratched the back of his head again, staring at the floor.
"Well, you might want to, um, check your tongue," he said. Her eyes widened and her hands flew to her mouth.
"Why?" she asked, her voice muffled.
"Well, I mean, I don't think I got it, but-" he started to say, but Fionna cut him off.
"Don't think you got it? Wait- You don't mean... Marshall, if my tongue is white, I'm going to kill you!" She ran up the stairs, and he heard her open and close the bathroom door.
"Technically, you can't kill me," he called up to her, floating towards the bottom of the stairwell. He heard her emit a surprised squeak, and he winced. Crap. Way to make things awkward, broski. "Marshall!" Fionna came thundering down the stairs, her hands still over her mouth. "Marshall, you- You idiot! My tongue is white! Look," she said, sticking her tongue out.
Marshall burst out laughing- her tongue was, in fact, bright white.
"It's not funny!" Fionna said, blushing. "Fix it!" Marshall stopped in mid-laugh, falling from where he was floating and banging his head on the floor.
"Fix it?" he asked, sitting up and rubbing the back of his head.
"Yes," Fionna said. "You're the Vampire King, and it's your fault, so fix it!"
"Um..." Marshall tilted his head, still sitting on the floor. "I don't know how." Fionna glared at him.
"Find a way," she said. "I am not going back to Cake like this, she'll think we were-" Fionna stopped, her face going red again.
"Think we were... what?" Marshall asked quietly. Fionna went even redder, and turned away from him.
"Nothing," she lied. "It's nothing." She steeled herself, then turned back around, only to come face-to-face with Marshall.
"You know what I think?" he whispered, sliding his hands down her arms until he had a firm grip on each of her wrists. "I think," he said, so softly Fionna barely heard him. "I think that you were going to say that Cake," he leaned closer to her, his lips practically touching her ear. "Would see your tongue," he turned his head, so that his lips actually did brush her ear as he spoke. "And think that we had been-" his statement was interrupted by Fionna kneeing him in the stomach.
"Dude! What is with you tonight?" Fionna asked angrily, standing over him. Marshall was rolling on the floor, clutching his stomach and moaning. "I mean, seriously, first you try to bite me, then you 'accidentally' suck out all of the red in my tongue, and now-" she hesitated, staring down at him. "Why're you acting so weird, Marshall?"
The vampire propped himself up on his elbows.
"Maybe I have an oral fixation," he said, grinning. Fionna rolled her eyes.
"I'm serious, dude. What's up?" she asked, nudging his side with her foot. Marshall rolled over, floating upwards until he was at eye level with Fionna.
"Maybe I'm just... Distracted," he said softly. Fionna frowned.
"By what? There's nothing here to be distracted by but m- Oh," she said, her eyes widening as she realised what Marshall had meant. "You mean... Me?" she asked, blushing. Marshall set himself down lightly, taking a few steps towards her.
"It's always been you, Fionna," he whispered, cupping her face in his hands before his lips came crashing down on hers. He pulled her closer to him, one of his hands going to the small of her back and the other gently threading its way through her long, blonde hair. Fionna's hands found his shoulders, her fingers digging into his back as she gripped him tighter.
"M- Marshall?" she stuttered, gasping as he moved his mouth along her jaw line and down to her neck.
"Mmm?" he purred, the vibrations of his throat sending an absolutely brilliant feeling out from where he was nuzzling her clavicle.
"Well," Fionna said, tilting her head to allow him better access to the junction between her neck and chest. "I was just- ah!- wondering what you were," -she inhaled sharply as his teeth grazed her skin-"What you were planning on- oh!- doing," she twisted her fingers into his dark hair, arching her back and keening as his long fingers slid down her back, tracing her spine before nimbly lifting the bottom edge of her shirt and pushing it upwards, exposing her stomach. He kneeled in front of her, planting a rather sloppy kiss at the bottom of her ribcage before sitting back on his heels and gazing up at her.
"You," he said, "Are incredibly beautiful, you know that?" Fionna blushed.
"You think so?" she asked him, pushing her bangs out of her eyes. Marshall smiled, standing up again.
"I know so," he said. "And just so you know, the answer to your first question was 'You'." He grinned at the momentary look of surprise that crossed her face before he kissed her again.