A/N: Yo! I decided to contribute to the Adventure Time fandom for once, and try my hand at a Bubbline (or just implied Bubbline) oneshot. I hope it's somewhat enjoyable! It wasn't exactly what I expected to when I finished; but I like it. Feedback would be appreciated, because I'm very unsure about this. I'd love to hear your thoughts about this, please. If you see any errors, please tell me that too! :)

Chemicals bubbled warningly in a beaker, a noxious mix that was possibly radioactive due the acidic green glow it emitted. Vials and tubes rested on racks, as spotless and clean as the tidy, alabaster lab. Mumbling could be heard should one dare enter the candy princess's lab—but considering the occasional explosion that went off many found themselves inching away at the prospect.

However, one person was an exception.

It was night out, leaving most of Princess Bonnibel Bubblegum's citizens tucked away in their candy beds, dreaming of even more sweet realms. Bonnibel fussed over a stack of papers that floated to the floor, covered in algorithms and formulas that would have many at a loss. As she bent down to pick them up, she missed the shadow skulking about the walls and ceilings, fading into thin air.

"Errgh, I know I'm missing something," Bubblegum stood, frowning as she looked over her experiment. The color was off, the smell too rank, the texture and quality too alike vomit and twice as thick. Her lab coat swished as she paced around the table, taking a stand in front of it and looking at an array of other ingredients. "Perhaps the saliva of a sphinx?" She directed her attention to a thick, glistening fluid. She bit her lip, before going over her notes. Nodding to herself, she poured a single spoonful into the vomit looking concoction. It gave off a colored puff of smoke and gurgled as it shifted. "Glob, it's so close. . ." she said, huffing. "But not perfect."

She went to her notebook, oblivious to the shadow creeping towards her, and jotted down some notes after she set the beaker down. She placed a pink thumb between her teeth and chewed. Eyebrows furrowing in concentration, she carefully grasped her experiment's container and turned around.

She blinked and a pale gray face, red eyes leering and sharp teeth glinting in a horizontal crescent moon smile, suddenly appeared right in front of her. With inky black tendrils wriggling about, the scream did Bonnibel in.

"Boo!"

The princess shrieked, jumping. "Marceline, you dung nugget!"

Despite her firm grip on her incomplete experiment, the sudden jolt to Bubblegum's arm when she bolted into the air had the nasty mess of science-y stuff spilling into the air and splashing the cackling vampire in the face. Marceline only had a moment to widen her eyes, subsequently shutting them quickly afterwards, as she hovered in the air, clutching her sides from her previous mirth. She yelped when the spilled concoction slipped into her throat as she inhaled.

Marceline dropped, bum hitting the floor roughly as she sputtered and coughed. Bonnie stared at her reproachfully, a glint in her eye showing the concern she was unwilling to display to the rowdy, millennia old girl.

"Ech, yuck, ew, sick!" Marceline bit out, a grimace on her face as a gray hand rubbed at her throat, tongue sticking out in distaste. "What was that crap, Peebs?"

"That," Bonnie glared, "was my experiment. That you ruined." Pinching the bridge of her nose, Bonnie sighed. "Glob, and I spent so much time gathering the ingredients, too." Seeing the ugly colored fluids still dripping off of Marceline, she tugged the girl up and demanded her to rinse it off. "The experiment was incomplete, and untested, so you shouldn't chance it. I have no idea how it will affect you." Frowning, Bonnibel eyed the vampire, who she noticed was actually shorter than her when on solid ground. "Did you swallow it?"

Marceline rolled her eyes. "Yeah, but not like it matters; I'm already dead, remember?" She winced when Bonnibel not-so-gently slapped her arms. "Ow, Bonnie—what was that for?"

"For being a careless fool, for one." Bonnie replied wryly. "No matter how many times I tell you, you still endeavor to disturb me when I'm working." And worry me in times like these. Shaking her head, she went to retrieve a rag to help clean of Marceline.

Marceline huffed, ignoring the slight pain she felt at those words. Or maybe it was from the tingly, pins and needles kind of sensation that began to grow in her chest. Rubbing at her skin uncomfortably, she averted her gaze from the candy princess. She couldn't leave the princess alone as much as she could ignore the fact the sun was dangerous to her. Perhaps Bonnie was too, with the way her words always stung and how sometimes just looking at her could make her feel all warm and tingly and hot and how sometimes she worried her unbeating heart was pounding hard enough to break out of her ribcage.

Or wait, she wasn't looking at Bonnie right now so why—ow, okay, ow. That itched. And burned. Oooh. Biting back a whimper and arching her back, Marceline attempted to call out to Bubblegum as the candy princess left the room. All that escaped her throat was a weak whimper, perhaps a hiss. The room swirled and Marcy's eyes unfocused. She felt helpless and scared, and suddenly so very small. It lasted all of a moment before she collapsed in a heap with a strangely muffled, light thump signaling her meeting the floor.

Feverishly, she wondered why she felt like she was bundled up in a ton of clothes. Everything was dark and she felt trapped. She struggled weakly, wondering what confined her. Then she stilled, breathing heavily. She felt fuzzy, in more ways than one. Shutting her eyes, she felt the chill of the floor seep through her current prison. Delirious, she was quickly lulled into unconsciousness by her own stuffy breaths and the shock she experienced.

Returning with two towels, Princess Bubblegum entered the room only to blink. "Why that litt—" she growled. Marceline had left her. Did she have no concern for herself or any clue as to what could happen from the exposure to her experiment? Bonnibel felt worry churn in her gut, though she would never admit it. When she next saw Marceline, she be sure to make her displeasure known, verbally. Or with silence. Marcy absolutely hated it when she was ignored. She'd deserve it for making Bubblegum stress over her. Scowling, eyebrows furrowed in concern, she made her way to the mess behind her lab table.

The moment she rounded the corner, her analytical mind immediately caught that something was off. Her senses tingled. She stopped and glanced down. "What the—" she broke off. She bent down, thankful that her hair was in a ponytail so it wouldn't fall into her face. Looking at the lump, she correctly guessed these were Marceline's clothes. The red flannel she wore, the pair of pants and her shoes. . . what were they doing here?

Gnawing her lip, she stared at the pile with her gut aching in upset. Something happened to Marceline—or this could be another bid to mess with her head or send her into a screaming fit. Was that childish vampire running around in the nude? She flushed at the image, cheeks heating up as she rapidly shook her head, logic removing the theory. It was unlikely. She was quickly becoming alarmed. "Marceline," she called aloud, standing but only taking her sight of the clothes long enough to scan the lab. Frowning in dread, she repeated loudly, "Marceline! If this is a joke it's not funny. . ."

She fidgeted when she was met with silence. Her jaw tightened and she stooped down to gather the clothes. Holding them in her arms, she realized very quickly that these were not just Marceline's clothes. Something inside Marceline's shirt shifted, twisting, emitting warmth. It was soft, somehow. A indecipherable noise sounded from the flannel.

She jerked but managed not to drop the thing in her arms, hidden from her vision. Cautiously, she stepped forward and set the lump onto her lab table. For a moment she did nothing but stare as she caught the signs of something breathing. Funny, it made her think of Marceline. Marceline breathed out of habit, because she wanted to taste the air, smell the scents.

She mentally kicked herself for getting sidetracked. Okay. Time to find out what this thing is. . . But she had a clue. Marceline's absence, clothes left on the floor, and something laying within them? Oh Glob, I hope it's not a baby. I do not want to handle that.

With shaking hands and a bead of melted candy slipping from the pores of her forehead, she grasped Marceline's shirt and steadied herself. What if it's naked? Of course it'll be naked you're taking off her shirt! Blushing furiously and swallowing thickly, she pried the fabric off.

She blinked blankly.

A small head of black wobbled in the air at being disrupted from a nap. Red eyes blinked fuzzily and stared up at Bubblegum.

"This. . . might be a problem." Bonnie said. "Marcy?" she tried, hesitantly. She caught the gleam of recognition and intelligence in those red orbs.

Marceline looked at her in confusion, before going to stand. She blinked when she toppled over, unable to float or stand on two legs, and hissed in surprise when she suddenly caught tiny furred arms moving in place of her normal limbs. "What the muffin, dude?" she attempted to exclaim, because this did not feel like a time where she shapeshifted in her sleep. What actually left her mouth was a furious mewl. With wide eyes and pointy, fluffed ears pinned back, she fixed on Bonnibel who was trying, and failing, not to smile. Marcy glared.

"Don't look at me," Bonnibel finally giggled, because how could she not when the vampire queen was reduced to a mere fluffy black kitten and was glaring at her with big, adorable eyes? "You're the one who messed up my experiment. I warned you."

Marcy's expression all but demanded that she fixed this. The kitten vampire hissed threateningly, or tried to. She startled when tender pink hands scooped her up and hugged her to her chest. "Aw, you're so adorable!" Bonnibel teased, smirking slyly at the offended and embarrassed look her aggravating best friend managed to convey with her feline features. She had to say, Marcy was really soft. She stroked Marcy's sleek, long fur, threading through it easily.

Marcy fussed in her arms. Surprisingly, she didn't use her claws although Bonnibel was sure she knew how to. With her miniscule strength in this form, Marcy was helpless, something both realized quickly. The snake of pure fluff that was Marcy's tails flicked in agitation.

Marcy couldn't believe this. Here she was, the embodiment of awesomeness and all that was wicked cool and rad, cuddled up into Bonnibel's chest as a kitten. A kitten. It was blasphemy, a heinous set up; it had to be. In any other circumstances, she would be secretly reveling in such physical affection from her pink princess, but this was too much. She hissed venomously and pouted, unintentionally looking cutely sullen.

Keeping a firm, gentle hold on Marcy, Bonnibel decided that she wouldn't start on the antidote just yet—the effects of the potion she was creating was supposed to be short term anyway seeing as she kept that in mind the whole time—so she figured she would enjoy this while it lasted. But she would definitely need to keep Marcy here in case something happened. Marceline didn't appear to have carried any of her abilities over into the small kitten body she adorned, judging from the fact she had tried various times to float out of her grasp or escape.

Marceline mewled in surprise when she found Bonnie leaving the lab, still cradled to her bosom. Thank Glob she had fur, otherwise Bonnie would surely catch the bruising of her checks, phantom heat turning them violet. Maybe she could enjoy this, but she sure as all fudge wouldn't show it. She huffed, miming dissatisfaction in Peebs' arms as she flailed a little bit. The pink fingers that scratched at her ear had her stop in an instant. Sauntering up the stairs, Bonnibel filed away the fact Marceline was purring—which was absolutely adorable—in the blackmail corner of her brain (and secretly into the section of all that was Marceline) and stepped inside her bedroom yawning. The guards had eyed her speculatively, wondering what sort of science she used to spawn the disgruntled cat, but thankfully for Marcy's pride should she be discovered, didn't ask.

Setting the helpless cat onto her bed, she gestured for her to stay. "Until the effects wear off," Bonnie received a glare. "Oh stop it, I've told you enough times to be careful in my lab since you never listen to me when I say keep out of it. So, as I was saying: Until the effects dissipate I suggest you stay here so I can observe you in the case something besides the obvious difference in your body structure pops up."

Marcy's ears pinned back in displeasure, but then nodded surprisingly. While she didn't exactly like the fact she was stuck like this, at least it got her into Bonnie's room without her having to ask or having to sneak in. She grinned mentally, before a sudden urge hit her. As Bonnibel left the room to enter the bathroom, shutting the door so she could change for the night, Marcy lifted up her leg.

Bonnie hummed to herself, swishing a tooth-friendly paste she developed to keep her teeth healthy in her mouth as she brushed lightly. She spat into the sink quite elegantly and exited the bathroom, only to gape at the sight of Marcy.

"What the Glob, Marcy." she deadpanned, nose scrunching up in disgust. "That's just gross." And she filed this into the corner of her mind christened "All the Disgusting Acts Marcy has Committed".

Marcy just continued licking from the bottom of her leg up, smirking as much as any cat could, before dropping it and licking her paw to dab at her ears, looking oddly snooty from her perch on Bubblegum's pillows. Her tail swished lightly in contentment.

Shaking her head, Bubblegum pulled the curtains closed at the window to prevent the risk of Marcy being assaulted by the sun, assuming that her transformation didn't protect her. She yawned and turned out the lights, lifting the covers and displacing a hissing Marcy from her pillow as she plopped down.

Marcy narrowed her eyes at the candy princess, before realizing something. She snuck beneath the covers, squirming until she was on Bonnie's chest who blushed and growled, "What are you doing?" Bonnie lifted the covers to see an innocent black kitten peering at her, pawing at her shirt with an emotion she couldn't discern.

Oh.

Bonnie turned her head, flustered. Beneath her fur, Marcy blushed too.

Bonnibel didn't lie when she said she wore the band shirt for nightwear. It made Marcy warm, so very pleased and happy and glad. She purred embarrassingly, getting a smile out of the blushing candy princess.

"I told you," Bonnie murmured quietly, rubbing Marcy's head. She could just feel how happy Marceline was, and seeing the vampire so happy always beckoned her heart to race quicker. "I wear it when I sleep." Marcy bumped her head into Bonnibel's hands. She would worry about being humiliated by her current actions later, but for now she was going to enjoy this moment that she shared with her candy princess. Bonnie leaned forward on her elbow and planted a kiss on Marcy's cold nose, garnering a shocked dilation of those endearing red eyes.

Eventually Marcy just blinked and settled onto Bonnie's torso, purring loudly, deeply, purple beneath her fur. She rested her head in the crook of Bonnibel's neck. Bonnie giggled slightly, fidgeting at the nose tickling her sweet skin.

Closing her eyes, Bubblegum smiled. The small warmth of Marcy's fur spilled into her; it was like she held a small, subtly fragile treasure in her arms. And perhaps unknowingly she did, considering Marcy had given Bonnie her silent, still heart a long time ago. In her own chest, it was dead, but in Bonnibel's hands it was so very alive, and strong. Marceline was certain it would only ever beat for her.

She'd never tell the Bonnie that, though.

Bubblegum shifted, feeling something of a dead weight resting on her. It wasn't uncomfortable, but something was off.

She opened her eyes only a sixth of the way and could see nothing but black. Raising her eyelids higher, she saw a head of wild, very much tousled and long hair, which slipped beneath the colors.

Her face was blank and she lifted the covers.

For a few moments she didn't comprehend it, but when she did. . .

"Eeee—!" she shrieked, shoving Marceline off of her and onto the floor, gaining an "oof!" of disorientation from the vampire. Marcy rubbed her eyes and growled, glaring at a flushed Bonnie who shut her eyes tight.

"What the muff, Bonnie?"

Shakily, Bonnie just pointed at her and mumbled something.

"What?"

Peppermint Butler burst in, a question on the tip of his tongue dying. He stared at Marceline, who arched a black brow at him. "Wha-wha—" he sputtered, turning entirely red. He looked back and forth between Marceline and Bonnibel. "Oh, I didn't—that is—I apologize for interrupting you Princess!" With that, the mint candy shut the door quickly and loudly.

"What is with this morning," Marceline groaned in bewilderment, rubbing her bum. Why was the peppermint acting like that? Usually he's all up on her case or something. Then she realized something. "Sweetness! I can talk again!" she beamed, grinning widely. She glanced at Bonnie.

"Um, why are your eyes shut?"

Bonnie just gestured at her again, more forcefully this time, as well as she could without her eyes.

Finally getting the hint, Marceline glanced down.

Her pointy, non-feline ears heated up.

"Oh Glob I'm naked! Oh, oh; hey, butler dude!" she desperately called, realizing now what the diminutive butler meant when he said "interrupting." She grabbed the blankets from the bed and covered herself with them. "It wasn't like that! It, uh, it was an experiment! That's why I'm naked!" she cried. Then she paused and her cheeks bruised violet with her blush. "Wait, I said that wrong, it's—!"

Far down the stairs, a voice resounded.

"I DON'T WANT TO KNOW!"

Bonnibel just cradled her face, humiliated.