This is from a prompt I decided to fill (albeit very loosely) on tumblr yesterday evening, and I'm actually pretty pleased with how it came out so I thought I'd post it here. I really liked the headcannons I developed when writing this, so I may toy around a bit more with writing Phineas and Ferb in the future. Enjoy the story lovlies!

Disclaimer: I don't own Phineas and Ferb

Okay, okay, calm down. Isabella Sharpia Garcio, you need to calm the freak down. Take a moment and sit down and calm yourself down before going over what just happened.

Back pressed against the front side of the Flynn-Fletcher's fence, I close my eyes and take a deep breath, replaying the situation that just happened. What had started out as a normal day (as normal as it gets with Phineas and Ferb) had escalated quickly into the biggest disaster in my life since my mom took away my Black Keys CDs. Of course, I can't pinpoint quite when today went from normal summer day to worse than my aforementioned Black Keys disaster, so maybe it really didn't start off as a normal day. Maybe I just woke up crazy. But waking up was normal. Breakfast was normal. Getting dressed was normal. And yet sometime between breakfast and where I am now I ended up with an existential crisis that made me need to re-evaluate my entire life.

I always thought the day I told Phineas would start off big and grand. I would jump out of bed and brush my hand through my perfect hair (because of course I had no bedhead in these fantasies), announcing that today was the day I professed my undying love for Phineas. The sun would shine, I would sing about how excited I was, and everything would go my way, like I was in some sort of a Disney movie. I'd go to him, where we'd both declare our attraction and he'd do something elaborate, like turn into a half-horse and taking me for a ride around Danville.

Okay, so that last part is slightly childish for me to think about. I mean, it's already been several years since the infamous summer Phineas and Ferb built their backyard roller coaster; I'll be turning fourteen in a couple of weeks. I'm going to be in high school next year, which basically means I'm an adult. I need to stop fantasizing about ponies or fairies or the ridiculous notion that Perry is a animal superhero who battles skinny men in trench coats. If I want to prove my maturity to my mom so I can be allowed to listen to all the cool indie artists the rest of the Fireside Girls are listening to, like Lana del Rey and The Arctic Monkeys, I need to stop acting like I'm still eleven—

Woah woah woah woah Isabella, you're distracting yourself again. Doing that thing you do where your mind begins to run a mile a minute in an attempt to keep from thinking about the real problem here. Focus, Isabella. Let's review what just happened.

Alright, so I walked into the backyard, like I do every summer morning. All was calm. All was normal. Phineas and Ferb sat beneath the tree like they always did, Buford and Baljeet and Gretchen (she's become a more constant factor this summer after she began crushing on Ferb) already gathered around them as well.

"Hey Phineas. Whatcha doin'?" I spoke my famous entry line as I joined the others. Phineas stood and pulled Ferb up with him.

"We have a big announcement today!"

There it is. I found it. Or at least, I found the place where everything went from peachy to the absolute nightmare they are now. Because when Phineas said that, said that there was a big announcement he and Ferb were making, somewhere in my silly little brain something went awfully, terribly wrong and Phineas and I spoke next at nearly the exact same time.

"Dad made a big sale at his store and we're moving!"

"I'm in love with Phineas!"

He stared. I stared. I could feel my eyes getting wider with every passing second. I felt my brain completely shut off as my pre-teen romantic instincts took over.

"Pack lots of photos!"

And with that witty and redeeming remark I bolted out of the backyard and slammed myself into the outside of the fence, staring at the blank patio where Mrs. Flynn-Fletcher parks the car as I had a minor mental breakdown over what just happened.

Yup, that just about brings me to where I am now.

"Isabella?" I hear Phineas yell from behind the fence.

"Shoot," I whisper and search quickly for a place to hide. There's a bush to my left and it's just as good as any so I dive into it and curl into a ball in hopes it shrinks me down. Hot tears of embarrassment stream down my face as I hope he won't be able to see me.

So he knows. I guess now is just about as good of a time as ever to let him know, but why, oh why did you choose to execute your confession that way, Isabella? Not only did you manage to throw him a complete curveball, but you also announced it in front of pretty much your entire circle of friends. You won't be able to show your face around here for weeks, if ever. Might as well just pack up and convince Mom to move to Alaska.

Wait a second. Wait a freaking second. Phineas is moving? As in, moving moving? Like, far from here? Far enough that I won't ever see him again?

Now the tears are from embarrassment and sadness, as I realize how awful life is about to get in Danville without Phineas and Ferb. I love the rest of our friends but God, that means I'll have to deal with Buford and Baljeet twice as much as I'm used to and ugh, we may even have to start hanging around that Irving kid in an act of true desperation.

But… I just can't wrap my head around a life with no Phineas. He's been such a constant for most of my life, someone I can always count on. The idea that he's leaving makes me want to stay curled up in this bush forever. It's nice and green and smells like nature and… it's moving. Why is the bush moving the only reason it would be moving is if someone else is trying to get in and the only other person who would do something as ridiculous as climb into a bush after me would be-

Crap.

As slowly as I can, I turn my head to my right and come eye-to-eye with the boy of the hour. I can feel my face set into a bit of a grimace as I prepare to apologize, but Phineas begins to speak instead.

"You know, when I was really little, back before even Ferb and Dad, I used to always hide here when I played hide-and-go-seek with Candace." He pulls a few leaves off the bush and twists them around in his hands. "She would always scold me for choosing the same place, but I never changed it. I never wanted to. Sitting here always felt safe, like I was in a bubble away from the rest of the world." He stops twisting around the leaves and lo and behold, in the process of about thirty seconds he's made an entire crown out of leaves from a bush. Because that's what Phineas Flynn does. He takes something mundane and ordinary and twists and turns it until something amazing comes as a result. He catches me off guard by brushing my hair out of my face and topping my head with the crown. "I'm not shocked because I already knew. I've known for a while now. And I want to do something about it just as much as you do. So when you're ready… So am I."

I blink in shock because he knows. He's known for all these years, all this time I've wasted trying to keep my crush and it's been for no use. And now I know that he knows I like him even more, because he's acknowledging his reciprocation but telling me I can do whatever I want about this relationship at my own pace, and suddenly I'm scared. I'm scared because I'm only thirteen and this would be my first real relationship and God I don't want to mess it up. I don't know if I'm ready for a grown up relationship at all, actually, because it's one thing to be mature enough to listen to Lana del Rey but it is quite another to be mature enough for a relationship.

He sees me sitting in shock and is he trying to kill me of shock today, because get this, then he leans in and kisses me on the cheek. And before I even have time to react he speaks again.

"We're not moving far, by the way. We're building a house on the empty lot just up the street. I want you and the others to help me and Ferb design an awesome room where we can all hang out."

And holy freaking cheese this has been the wildest thirty minutes of my life, because now I know that Phineas knows I like him, and that he likes me back. I know that I have the power to have a relationship with him on my own terms. And I've been kissed on the cheek and the empty lot just up the street Phineas is talking about is next door to my house, which is probably the same distance from his house's spot right across the street right now but whatever, I'm still counting it as a victory. And I realize I'm about to enter a whole new world, a new era of Phineas and me and Ferb and the rest of my friends, a wonderful new time where I'm so, so happy, the happiest a thirteen year old could be. And I sit in that bush for a long time, smiling to myself and telling myself Okay, okay, see? Everything worked out just perfect in the end.

I have a lot of fun writing Isabella, because I can see her ending up much like I am now. A seemingly put together girl on the outside but a blabbering mess on the inside. She'd definitely be the kind of girl with a fandom tumblr!