I've seen a lot of stories where fionna meets Flame Prince, but they were lazy and only copied the episode and gender swapped. I believe the genderbend characters should still be individual so this is how I think the couple should meet.

enjoy!

the cool breeze drifts through the air. Gumball is sitting on the leafy roof of the treehouse base of our favorite adventurer.

"...and through my studies in cloud seeding, I have created," the colorful rocket he is holding lights and shoots off into the sky. It explodes into fireworks of yellow, green, pink, and blue. The one difference is that, while normal fireworks have sparks that disappear and never hit the ground, the sparks continue to rain down and splatter across Gumball's umbrella as he finishes "liquid pyrotechnics" fionna feels enthralled with his discovery.

"cool." Says cake, purring on his lap.

"thanks, kitty." Says Gumball

"what do you think, Fi?" Asks her cat. Fionna only blushes and scoots toward Gumball

" It's amazing" she wistfully peers through her bangs at her crush. Why could cake rest in his lap so easily? Maybe she could...? She leans her head against his shoulder

" erm, no Fionna. Don't be weird." he gets up and walks down the ladder "I'll see you two later" Fionna just sits there with a trembling lower lip.

she spends the rest of the day weeping in her room, surrounded by pictures of PG and cuddling a lock of gummy hair. Why doesn't he like her? I save his butt so often and he is grateful for it, but what does he not like? Her personality? Her looks? Does he only hang out with her because he wants to study the exotic traits of a human. He probably thinks she looks to weird with her peachy skin and blonde hair. This makes her feel angry! Man, she needed her friend Cake now.

"Cake?" There was no answer. Where had that girl go? Fionna sighs and sits to play BMO, imagining all the villains to be PG.

CAKE

cake felt so sorry for her poor friend as she sat their blubbering over some guy.

"I know! I'll just find Fi a new guy!" she sets off with her red heel boots and walks through the woods away from the treehouse.

soon she hears a bass tone yell and has to fight some owl knights to save a guy stuck in a bucket.

"your safe now bucket prince! Wait- Firita? I thought you were a-"

"prince? I have been practicing!" The small bunny shaped flame giggles in her normal voice.

"well, your pretty plugged in, do you know any princes Fi's age?" asks cake

"I know just the guy! He is only a few months older, and he is way hot!" They set off and (after a well placed time lapse) arrive in the kingdom of fire.

"Firita, ill surely die if I take a step in that place! Nuh-uh girl!"

" here.." She mumbles an incantation as a blueish hue pours over Cake's fur.

"I cast flame shield on ya!" She states. Firita rides on Cake's back as they enter the castle atop the highest volcano.

"There's our man! He is in the lamp!" Sure enough a boy the age of either fourteen or fifteen sits iban large oil lamp hanging from the ceiling. He seems very bored bouncing a fire ball against the glass.

cake sees the boy's mother sitting in a throne at the center of the large room. Presenting her self rather snootily, Cake politely asks for the flame prince to date her boss, princess Fionna, ruler of the grasslands

" what does your employer do every day?"

"she goes out and kicks butt!" Cake winces, "I mean, she is a warrioress, my queen."

" How wondrous! I see her very fit to date my- "she slashes the rope holding her son above their heads and he comes crashing down. He steps out of the pile of glass and walks over towards cake.

"EVIL son!"

"take me to my suitor." He states.

"wait, you seem normal." States cake.

"why do you assume I'd be anything but?" His body erupts into more flame, concealing his handsome face and Mohawk style hair into the face of rage and evil. "AM I NOT GOOD ENOUGH FOR THE GRASSLANDS?" He blows up at her.

"oh, look. I have a message from my princess to cancel this meeting. She doesn't want to date you, sorry hon." Says Cake nervously.

"WHAT?!" Screams the prince. He resumes to chase her to the treehouse.

FIONNA'S POV

I hear a loud crash and come running to investigate. I see poor cake fly at me looking terrified

"Fi! Fi, you have to help me! It's- just then an orange and red flame swipes across the window. Soon the house begins to erupt in flames.

"WHO LIT THIS FIRE!"I yell, staring at the flames destroying my precious Gumball pictures. I cuddle the hair to my chest and run outside.

"I'LL KILL YOU!"

i see a figure whooshing by the rockets Gumball left.

"DONT YOU TOUGH HIS STUFF!" The clouds become an angry grey as I try to run up there to smother the flames. in a quieter voice I state somberly "if I can't have him, I at least want his stuff to comfort me." the rockets go off anyway and as their liquid cascades down from the sky I hear a piercing cry as it extinguishes the fire. I see an angry looking boy turn to me and I whip out my looks to himself being drenched and doubles over in pain. He falls and my hero instincts kick in. I run and catch him in my arms. We tumble off the roof but I stick my hand out just in rooms to grab the window frame. We are thrown inside with me underneath this boy. I curiously turn up his chin to get a better look at his face. He is... Cute. Suddenly, in the dry environment he light again, singing me. He pulls away with a glare that somehow makes me feel very sad.

"why do you not like me? What is wrong with me?" He spits at me.

"I-I don't know what your talking about. I do like you though. Well, I can't really like you if I don't know you so..."

"Typical women! Changing her mind! I will leave now!" He rushes toward the door, leaving a trail of burnt grass and fire.

"who was that?"

"the prince of the fire kingdom." States cake nervously. "His mom said he is evil."

"we'll then we have to follow him! Come on!"

they set off to finds the evil boy as to make you're he doesn't destroy anything.