A story I wrote up on Tumblr for three reasons; I needed a fubbline story, I wanted to do some 'Finn in a dress' stuff, and my good buddy Kasumisty suggested 'bet over Finn wearing a wedding dress at their marriage' as a prompt. I think it came out pretty good.

Disclaimer: I don't own Adventure Time or make any profit off it.

Finn's parties had many side effects, not the least kindling a friendship between Bubblegum and Marceline thanks to him, and as time went on, the friendship between him and Bubblegum and Marceline had grown to a surprising degree of comfort between them.

His crush on Bubblegum and Marceline ensured that he was prone to listening to them and mindlessly doing whatever either of them told him to, and quite by accident, as time had gone by, he had become something of a protégé to them, and he was aware that the two women were planning something (always meeting behind curtains and talking in excited voices and giving Finn meaningful looks and grins whenever he noticed them at it; Finn didn't understand it, and before the two women came over to drag Finn off to whatever scheme they had planning, Jake warned to stay on his toes, ladies with plans were really scary), but he wasn't sure what.

Somehow, this soon lead to them having a sleep over at Bubblegum's castle, something that was a bit of a childhood thing. Finn was happy to do it; he loved hanging out with his ladyfriends, and Bubblegum and Marceline seemed to recapture something of their childhoods they'd never had the chance to have. Finn didn't know this, he didn't know that Bubblegum had been 'born' as an adult several centuries ago and unaging, while Marceline had spent all her time surviving and struggling and never had the chance to just be a kid.

They were really hyped about it, so Finn just went with it.

This was, for him, a theme whenever Bubblegum and Marceline had plans for him.

Bubblegum sat against the headboard of her bed, her impressively large bottom bouncing happily upon the bedspread and sending ripples through her body, wearing only a massive woman's T-shirt so long and big it was like a night dress. Marceline was leaning across the bed in a T-shirt and boy-shorts, face stained a lighter shade of gray by Beemo's bright light as she eagerly played a platformer, her forked tongue sticking out of her mouth. Finn, wearing much the same as Bubblegum and inexpressibly adorable for his unconscious emulation of his older friend and not seeming to mind that he was wearing girl's clothes, sat with his head happily encased by Bubblegum's large thighs and his hand resting on Marceline's shoulder.

The three of them remained quite close together, giggling and laughing and talking happily as the night had worn on. No fights, no servants, no other little intrusions from their normal lives; just the three of them hanging out and enjoying a rather intimate night together.

Finn giggled rolling his head into Bubblegum's leg, his ear squashing deeply into the gel-like softness of her body, and he smiled at the loud and insistent noises Bubblegum kept making, her cheeks blooming with deeper red and her hips surging up a little. "Ah, Finn!" Bubblegum said, breathing heavily. "Don't... ah, don't move so much so quick! Not until I tell you!"

"Sorry, Peebs-" Finn started, and Bubblegum hitched herself forward, and Finn squealed as her much larger body loomed over him like an incoming mountain, and his head merrily landed at the join of her leg and hip.

"Now," Bubblegum said, grinning intently. "You can move around."

Finn giggled, squirming around. He didn't understand why, but Bubblegum liked it, shaking around and grinning and making all kinds of interesting noises, hugging herself like she just wanted to cuddle something so bad she could explode with it.

Marceline laughed at them. "Stop being so cute, you guys! You're making me wanna quit and join you!"

Bubblegum smirked. "How intriguing! I dare you to do it!"

Finn perked up. Marceline's ears twitched. "Oh, a challenge, huh?" Marceline said, shutting off the game and turning around, every inch a hungry predator that had just been challenged by another, and a soft delectable young prey close at hand. She growled playfully, and pounced on them; Bubblegum and Finn giggled helplessly as Marceline rolled into them, the Vampire Queen snatching Finn up and tossing him into the air before she caught him, and Bubblegum giggled helplessly as Marceline rolled her shoulder and head into the Candy Princess' lap, the tremendous amount of flesh there more than adequate for the slimmer vampire to roll in there, clutching Finn in her arms and cuddling the smaller boy to her body.

She was so strong that though Finn struggled - even if he only put up a token resistance, not minding his Vampire Queen holding him one little bit - he was totally helpless in her grip, and she could do whatever she wished to him. Marceline giggled and so did Bubblegum, both women finding the prospect of that extremely delightful. Finn blushed cutely, giggling helplessly.

Beemo quietly sat there and watching, hoping Finn, Bubblegum and Marceline would forget she was there and let her keep watching the fun. "You know," Bubblegum said, wiggling her head around so her glasses wouldn't slip off. "I really... I really like you guys." Her arms slipped down as she leaned forward, awkwardly aligning herself so that one arm went around Finn's head and the other on Marceline's shoulder. She squeezed them, smiling bashfully. "I really, really do!"

"Hee, hee!" Marceline leaned up and kissed Bubblegum on the cheek. She smiled shyly. "...Me too," She said, in a quiet voice implicitly saying that telling anyone that she'd said that, ever, would only involve their ultimate doom.

Finn cuddled into his women. "I like you guys... so, so much!" He giggled guiltily.

Bubblegum gave him an extra squeeze. He looked up into her eyes, smiling, and she giggled happily. He leaned around in Marceline's arms so he could tilt his face into Bubblegum's hand, and kissed her on the palm. Bubblegum giggled, grinning like a lovestruck loon.

Marceline hugged Finn even tighter, overcome with affection, and kissed him on the back of the neck; Finn wiggled around so his lips found her wrist, and both boy and woman hummed happily at the sensation, and Bubblegum giggled at how nice it felt to have them kissing on her.

As the night wore on, more innocent kisses (and some not so innocent kisses, between the women and as they tackled Finn from surprise, the boy too naive to realize what they had in mind for him as he would in later years) went between the three of them without playing favorites, settled into each other's company like they had been born for it.

Finn would have liked to party with his two favorite ladies in all the world, but he was young and not very good at sleeping through the night, and with startling insight, Bubblegum and Marceline tucked him into bed, rolling the blankets over him and around him. He yawned as they settled in under the covers, cuddling his much smaller body against their superior forms, their curves meeting his plump though underdeveloped body nicely. They cuddled up, like a love sandwich (Finn the meat of it, of course) and settled in for the night.

Bubblegum gave Finn a kiss on the forehead as he curled up, so comfortable with them to be hatless, and she eagerly sniffled his hair as he nestled up to her. Marceline put an arm protectively around him.

"Hey, Finny?" Bubblegum said, with an impish look.

"Humm?" he muttered sleepily.

"I really like you." She kissed him again, and for a moment it seemed that it was so intense that the only way for her to fully express her affection for him would be to swallow him whole but she wasn't big enough for it, so little play-kisses had to do.

"I really like you too, Peebs," Finn mumbled, and drifted back to sleep.

Marceline chuckled. "He's a cutie," she said fondly.

Bubblegum smiled. "Hey, Marceline?"

"Yeah?"

"Let's make a deal." She grinned menacingly, full of hunger and desire. "Our plan..."

"Yeah?" Marceline said.

"...When Finn marries us, I know how to decide what he wears."

"Do tell."

"Let's make a contest out of it. The first one of us who..." she coughed. "Claims his virginity, shall we say, gets to pick his outfit for him."

"Oh, the first lady who gets the Finn-bomb! Nice. If I win... um, I'll make him a sailor suit!" She giggled.

Bubblegum smiled. "And if I win, he wears a wedding dress!"

Marceline snickered. "...I like the way you think."

They shook hands, and sealed it with a kiss.

A few years later…

Marceline, and Bubblegum stood at an alter to Glob, in a lovely cathedral of precisely machined metal and robots ordained in the sight of Glob, both of them dressed in fine suits of black vests long enough to be coats, partly buttoned around fine white dress shirts and black pants adorned with so many belts as to constitute totally badass skirts, high boots below the knee and tipped from metal at the toes.

Between them, on the consecrated metal floor, plush plastic grass beneath their feet and made softer than clouds, Finn stood, still shorter than either of them and so chubby he looked like he was built for cuddling, plump and womanly in the surprising curves of his body. He stood demurely, wearing a grand dress in heroic colors of green and white, highlighted with yellow-gold at places. Soft and gauzy frills looped all around, connecting the poofy extensions of the sleeves and the hips, a massive train looped behind him and carried by Flame Princess (smiling wide and trying not to cry for her best friend's good fortune to marry such fine royalty, and she got emotional at weddings), Susan Strong, Lumpy Space Princess, and a few other people Bubblegum and Marceline couldn't bother to remember.

Peppermint Butler, Jake, and Ice King stood as the best man and giving-away figures to Bubblegum, Finn and Marceline respectively. Jake looked proud, Ice King stood taller than he normally ever did with a glimmer of the true Simon Petrikov standing firm through the madness of the frost, and Peppermint Butler… just sort of stood there. No one particularly wanted to know what he was thinking.

The crowd in attendance was big and wide, a testament to the lives changed and enamored of Finn, Marceline and Bubblegum. At the front, there was Finn's brother Jermaine, cheering for his brother getting married at last (and so young, too). Beside him there were the spirits of Finn's parents, Joshua and Margaret, and Joshua was happy to see his son married to such fine women though he had mixed feeling about him in a dress. Margaret shushed him, their little Finny looked so darling, and his brides so impressive. There were many princesses, sobbing that they had lost their chance at Finn but happy for him anyway. Lady Rainicorn floated overhead, directing the band that was playing for the wedding, and Bubblegum and Marceline gave grins at the sight of their old band mates from the Scream Queens; Keila, Bongo and Guy rocking it up with a metal twist, and while unconventional it certainly suited the cathedral.

As several of Jake and Lady's puppies ran in up, carrying the rings on a plush cushion and wavering with the weight of it, Bubblegum glanced at Marceline and winked. She giggled, looking down at Finn salaciously. She mouthed 'I win!'.

"Don't rub it in," Marceline muttered, but she was smiling.

Finn just smiled. As far as he was concerned, it was win-win.