AN: Crossposting from ao3 finally.


Isabella wandered over to the back yard of the Flynn-Fletcher house like any other day. Not necessarily an ordinary day, Phineas didn't do those, but it was a familiar routine by now. She sauntered through the gate with faux casualness, already ready with the usual "Whatcha doin'?" Except she didn't get that far.

Ferb grabbed her hand mid-syllable and dragged her over to Phineas, looking mildly concerned. On anyone else, this would have meant something small had gone wrong, but with Ferb? That slight frown meant he was extremely worried. He hadn't been this visibly upset in ages, and they'd been in mortal peril three times this month already.

Ferb pulled her around behind the tree and she saw why: Phineas was lying on the ground, conveniently out of sight, curled around his (weirdly large) belly and groaning.

"Phineas! What's wrong?" she exclaimed, kneeling beside him.

Phineas grabbed her hand and pulled himself off the ground to stare into her eyes. "Isabella, I... I'm going into labour," he whispered hoarsely.

"...What?" She wasn't sure what to do with that information. Or what he even meant by it, surely he couldn't be-

"He's pregnant," Ferb explained succintly.

"What."

Everyone present correctly interpreted her statement as one of disbelief, not as a request for clarity.

Phineas fell back onto the soft grass, gripping her hand tightly and breathing like he was running a marathon.

She took a deep breath. She needed answers. "How did this happen? Who's the father?" she asked.

Phineas shook his head. "I can't tell you, Isabella."

"But then..." she whispered, apprehension pooling in her belly. "Who's the baby?"

Ferb frowned at her, obviously discombobulated at her choice of question. It wasn't a normal question, she got it. But with the Flynn-Fletcher boys, nothing was really out of the ordinary.

Phineas clutched at the leg of Ferb's trousers. "It's you, the baby is you, Ferb."

"What the fuck," Ferb said.

"...How do you know that?" Isabella asked hesitantly.

Phineas grinned through his labour pains. "Remember that ultrasound machine last week? It works in colour now." He paused. "Hey, where's Perry?"

Isabella pointed. "He's lurking behind the tree."

"Oh, there you are Perry."

Perry chattered. Strangely, he looked almost... nervous. But he was a platypus, they didn't do much. Certainly nothing that would require nervousness.

"How is this even possible?" she asked.

Phineas stood up, one hand curled under his belly. "I guess the only way you can understand..." He paused dramatically, striking a pose. "Is through song."

~song montage~

Stage lighting shone down out of nowhere (literally nowhere, she looked), highlighting Phineas's strikingly pregnant form.

"Well I was sitting alone in the middle of the night

all bored with nothing to do

I called up a friend he put some stuff in my end-"

Ferb turned and walked away, an expression of utter disgust on his face. What passed for utter disgust through his usual lack of expression.

Isabella grimaced, tempted to follow. As much as she liked Phineas, there were some things she didn't want to know either. Not yet at least. But she held back as Phineas ran after his brother.

"Ferb, hey Ferb, bro, come back!"

Ferb sighed audibly, turning back to face them. "This had better be good," he said, in a tone that conveyed how utterly Done he was with this entire line of conversation.

Phineas seemed to not hear him, grinning manically and looking between the both of them (and Perry). Then he ripped off all of his clothes for some reason, revealing a fancy tuxedo underneath, complete with a tall top hat that had absolutely not been there before.

~song montage again~

"I'm having a baby and the baby is you-"

"You forgot your backing music," Isabella said, interrupting him.

The reminder stopped Phineas in his tracks and he flopped onto the ground, dejected. "Oh, what's the use!" he wailed dramatically.

Isabella glanced at Ferb, and he nodded slightly. Time to question him again.

"So who was this guy anyway?" she asked, folding her arms. Ferb came up next to her, silently asking the same question.

Phineas glanced around like he was hiding something. "...Doctor D's boyfriend," he whispered.

Isabella raised her eyebrow in what she hoped was obvious skepticism. "The teal-haired guy?"

Phineas nodded mutely.

"But- what- why-" She cut herself off, taking a deep breath to calm herself. "He's an adult, Phineas!"

"And he's Doctor D's boyfriend," Ferb added.

Phineas waved his hand dismissively. "Doctor D's cool with it, it was his idea."

"Doctor D's idea?" Isabella asked. "Phineas, you know what his ideas are like!"

Phineas's reply was, in hindsight, completely expected: "Totally awesome!"

Ferb's expression didn't change.

Isabella couldn't repress a sigh. Sometimes she wondered what she saw in him. "No. No they're not."

And then Phineas pulled off his clothes again, revealing nothing underneath. Just bare skin. "Someone get this baby out now!"

Isabella blinked in surprise. This was not how she'd expected her first time seeing Phineas naked to go. For one thing, he wasn't a centaur. But she was a Fireside Girl, she could handle anything.

"I'll do it, I got my Midwifery Patch last week," she said. "But first..."

She took a deep breath.

~song montage yet again~

"Once upon a time, on top of a mountain,

a baby was sitting in a water fountain..."

"How is that relevant?" Phineas asked, from where he was suddenly lying on the ground again.

Isabella stopped. "I... don't know."

Beside her, Ferb facepalmed.

She was spared from further questioning by Candace stomping loudly out into the yard, phone clutched tightly in one hand.

"Alright, what's all this noise?" Candace demanded.

Isabella glanced between the teenager, and where she was kneeling between a naked (!) Phineas's legs to deliver the baby. "Phineas is giving birth?" she tried.

"And it's a musical," Ferb added.

Candace narrowed her eyes and turned, marching back into the house. "MOM! Holy fuck!"

"Candace, what have I told you about swearing?" Linda asked, voice carrying through the air.

"But Phineas is having a baby!"

Linda's sigh was audible even over Phineas's grunting. "Candace, Phineas can't have a baby, he's a boy."

"But Mom!"

"Are you sure your pregnancy isn't making you delusional? Well, more than usual..."

Candace stormed out again, muttering under her breath.

"You're pregnant too?" Isabella asked, looking up at Candace. She wouldn't have guessed, since Candace still looked as slender as usual. Maybe Phineas had made something for her to hide it. He was thoughtful like that. "Since when?"

"I don't know," Candace moaned, sitting down on the grass and resting her face in her hands.

"Last summer," Phineas supplied, taking a break from the wheezing and groaning.

Perry waddled over, making his usual platypus noise and resting his head on Candace's knee. If Isabella squinted, she'd just about think he looked apologetic. Which of course was ridiculous, platypuses still didn't do much, especially not anything they'd have to apologise for.

Candace shoved him away. "Ew, get your stinky pet away from me."

Perry made his growly platypus noise again and wandered back over to Phineas. Within moments, he was clutched in Phineas's arms, tight enough that he almost seemed to be struggling to breathe.

"Candace, will you have these babies with me?" Phineas asked, oblivious to his pet's predicament.

"W-what? Phineas, I'm your sister."

"I don't care."

"What the fuck," Ferb said again.

"Come on," Phineas pleaded.

Candace sighed. "Alright, fine. But I'm doing a song first." She stood, walking over to the stage by the tree that absolutely hadn't been there a second ago.

The lights went out.

~another song montage~

Isabella waved her hand in front of her face, because that's what one did when plunged into sudden darkness. Of all the things Phineas could have done, he just had to find a way to turn out the sun. For dramatic effect, she realised, as a spotlight shone down on Candace.

The other girl had managed to change into a ritzy ballgown during the brief darkness, sparkling so distractingly in the spotlight that Isabella didn't even realise Candace was singing for a few seconds.

"You may have played me but my heart waylaid me

I wanna be your baby mommy too," Candace crooned into the microphone that had also appeared out of nowhere. That's when Phineas joined her on stage, somehow wearing his normal clothes again and not looking like someone going into labour at all.

"I can't believe they're both pregnant," Isabella whispered to Ferb, only half paying attention to the stage.

Ferb raised an eyebrow at her.

She shoved at his shoulder. "You know what I mean, Ferb. Is this a family thing? Are you going to get yourself pregnant?"

Before she'd even finished speaking, he was shaking his head in the most emphatic "no" she'd ever seen from him. "I'm only legally related to them."

"Right, step-brother," she said, nodding.

On the stage, Phineas dramatically slid onto his knees, accompanied by some fancy lighting that absolutely didn't have a light source. At this angle, Isabella could see his pregnant belly.

She turned back to Ferb. "Except he said he's pregnant with you."

Slowly, but surely, his shoulders slumped. She wouldn't have thought the news was that upsetting to hear, but she hadn't realised just how... odd... the Flynn-Fletcher family could get. That, and she was fully aware of how much her crush affected how she saw him. Them.

Perry waddled back over to them, bumping against Ferb's ankle like a particularly lazy cat and chirring.

In the quiet, she was able to make out what Phineas was mumbling.

"-And besides, incest is disgusting and um, anyone that condones pedophilia or incest is, um, bad and they should see a psychiatrist, and also, will you marry me?"

"Yes!" Candace said, tossing the microphone away.

The midday sunlight turned back on as Phineas kissed his sister, who was now also naked for some reason. There was a lot of tongue involved.

Ferb blanched, looking away from the two naked incestuous pregnant minors (also known as his siblings) making out on the lawn.

"Ew, gross," Isabella said.

"You don't understand our love!" Phineas wailed.

"Phineas, you wouldn't know love if it smacked you in the face," Isabella retorted, as she smacked him in the face.

Baljeet's voice rang out. "Phineas, I am going to eat your baby!"

"NOOOOOOOOOOOOOOOOOOOOOOO!" Phineas yelled.

Candace snuck away behind the tree to put her clothes back on while he was distracted.

Buford laughed and walked in, Baljeet under one arm. "You fell for it!"

"I do not think it was funny," Baljeet pointed out.

Something didn't add up. "...How did you know he was pregnant?" Isabella asked.

"You guys have been singing about it all day," Buford replied. "I'm surprised your mom hasn't heard you."

"She never listens," Candace said with a whine. "Besides, she's in the sensory deprivation tank with Dad."

Phineas stood up, waving his hands wildly. "You're not getting my baby!"

"Phineas, no one is going to eat your baby," Baljeet said. He paused. "Well, Buford might."

"I am feeling hungry..." Buford agreed.

Phineas shrieked, holding his hands up in a cross as he backed away.

"He's not a vampire, Phineas!" Isabella said, putting a hand on his shoulder. "You don't need to do that!"

Phineas turned around, still shrieking.

"Ow!" She pressed her hands over her ears, trying to block out the unearthly sound. "I'm right here, Phineas!"

After a few seconds of screeching, Phineas ran out of breath, falling back onto the ground with a thud.

Isabella opened her eye a crack, wary that he may be playing a prank on her. He hadn't before, but she knew that was no guarantee of anything. After all, he hadn't built a rollercoaster through the middle of Danville before last summer.

That's when Candace went into labour.


Ferb woke up. "What the fuck." That was the strangest dream he'd had for a while.

He glanced around for Perry, but the platypus was missing.


Perry was, in fact, sitting in his lair, being admonished by Major Monogram.

"-How could you, Agent P?!"

Just offscreen, Carl the Intern coughed. "There's no rule against it, sir."

Unsurprisingly, this information did not help. Major Monogram turned to face Carl, eyebrows furrowing. "Because I thought it was common sense to not get your host family pregnant!" He turned back to Perry. "What do you have to say for yourself, Agent P?"

Perry pulled his hat over his face in shame.

"They won't remember any of this," Monogram added. "We used the Amnesia-inator again. Your family has forgotten any of this ever happened." He frowned sternly from the screen. "This is your last chance, Agent P. The O.W.C.A. doesn't have the budget to keep cleaning up after you. Don't let it happen again."

Perry (still hiding his face) nodded, saluting.

A baby's cry filled the room, sounding remarkably like Phineas. "What are we going to do with these babies?" Carl asked, still offscreen.

Major Monogram didn't even look away from where he was staring Perry down. "Just send them to Doofenshmirtz."

"Sir? Are you sure that's a good idea?"

"He's not evil any more, he has the time. And Agent P will keep an eye on him. Won't you, Agent P?" The unspoken "they're your responsibility too" hung heavy in the air.

Perry slumped onto his desk with a sigh. It wasn't like he had much choice.

"Congratulations, Agent P, you are now a father. Unfortunately, the O.W.C.A. does not offer paternity leave, so we'll be expecting you here for work tomorrow."

Carl cleared his throat. "How did Candace-"

That was something Perry didn't want to have to explain to his superiors. So, to avoid that entire minefield, he fled, leaving his chair spinning behind him.

"Why did he- Oh," Carl groaned, continuing to exist just out of frame.

Major Monogram blinked, turning away from the empty chair. "Carl? What just happened?"

"You don't want to know, sir."

"Tell me, Carl."

Carl resolutely avoided Monogram's stare. "Well, sir, remember when Perry was in disguise as a teenage girl?"

There was a pause as Monogram mulled this over. Unnoticed by either of them, the chair came to a stop.

Then:

"You were right, I didn't want to know."


Everything continued on as normal, or near enough, until a few days later when Heinz accidentally lost the babies in a time travel accident.


AN: If you made it this far, congrats. If you're looking for an explanation (and/or a source for the lyrics), look up The Baby Is You by Toby Fox. The title comes from there too, as the most blatant hint I could as to the true nature of the fic.

Which means, yes, the summary's formatting was deliberate.

Feel free to concrit (how could I have made it more effective or in-character?), or tell me how much you hated it (go on, you know you want to), or, heck, anything else you wanna say about it.