"Candace, come on, honey. Today you're getting your hair cut, remember?"

Candace objected as she came down the stairs. "But mom, I know Phineas and Ferb are going to—"

"Boys, what're you planning on doing today?" Linda asked to the pair on the sofa.

Phineas and Ferb looked over to their mom and Phineas 'hmmed' in thought. "There's going to be a documentary on the world's strongest microscope we want to see! 'The head of a pin has never been so interesting'," he quoted with a smile.

Linda looked over to her daughter with an amused look. "Does that seem too terrible to you?"

Candace huffed in annoyance. "For the rest of the day they're going to—"

"I thought you were looking forward to this."

"Stop interrupting me! Phineas and Ferb are going to make a crazy contraption in the—"

"You can get whatever hairstyle you want, dear. Even that pink streak."

"Oooh!" the redhead exclaimed, excitedly forgetting about the rage that had flared from being interrupted again.

Satisfied, Linda began walking towards the front door. "If you two need anything, you'll have to call me, because your father's at the antique shop."

"Sure thing, mom." Phineas answered as Candace rushed outside, with Linda following at a more leisurely pace. He looked back at the show they were watching; the brightly coloured cartoon characters on it were currently singing about smiling. "Why are we watching this?" Without waiting for his brother's answer, he flicked through the channels, stopping on the Uncovery Channel.

However, as the minutes passed, Phineas began to find that he couldn't concentrate on the show. It was as if he had an itch he couldn't scratch; while possible to ignore, without distractions, it drove out his ability to focus. The niggling feeling resulted in him not being able to enjoy what he was watching, and he wasn't as discerning of his surroundings as usual, either. It was all very irksome for a boy that always wanted to be doing something.

It wasn't exactly new, though. He'd noticed feeling like this before, but it wasn't usually as prevalent in his thoughts as it was now. Phineas hadn't yet been able to work out why it was around—indeed, the extreme vagueness added to his annoyance about not being able to concentrate. He simply couldn't connect anything with it, not the time of day, the weather or the activity he was engaged in. Troubled by his mood, he found himself sighing, and then fidgeting and frowning. Unable to bear it for much longer, Phineas voiced his complaints. "Man… I'm feeling kind of down, Ferb."

Ferb very slightly turned his head towards Phineas with an accompanying sound effect (which happened to be rather ineffectual for the audience when in writing).

"That's just the thing. I don't know why. And I'm wishing there was something that could just… make someone happier." He thought briefly about being perked up by eating ice cream or watching comedy, but decided on doing something that would helpfully lead to a catchphrase. "Ferb, I know what we're gonna do today." He hopped down from the sofa. "Hey, where's Perry?" A few seconds ticked by in the advent of a long pause. "… Well, I guess the writer isn't going to bother with the B plot we usually have."

Outside in the backyard, the pair had gathered their usual mechanical equipment. Ferb was joining together two sections of metal together with a blowtorch (safely, of course), while Phineas was walking out of the garage with an armful of nuts and bolts in a box. There was a partially built machine already—at the moment, it looked like a tripod. This part was going to act as a stand to the finished product, as well as having lots of seemingly random science-y words to describe what made it work.

As was customary, Isabella was visiting the pair. With a smile, she opened the backyard's gate and wandered over to Phineas, while doing another thing that was customary: she asked, "Hey, Phineas. What 'cha dooooin'?"

"Building a happiness machine," he explained as he dropped the box by a blueprint that'd been lain on the ground.

"Oh?" she said with raised eyebrows and a questioning tone.

"Yeah, it's different from what we usually do—less fun, you know?—but I thought it'd be nice, because, what's not to like about what makes you happy?" he said, grinning.

She nodded in understanding and looked over to the tripod. "When do you think you'll have it finished?"

"Well, you know how these things go. Usually, we get it done during the time the show focuses on someone else if there isn't a montage. Conveniently."

Candace groaned. "Why did we have to go to Bobbi's hairdressers? He gives everyone the same hairstyle!"

"As I said, Candace, you can choose whichever one you want."

"Oh, come on! I can't choose from one thing!"

"No need to be ungrateful, dear. Do you want to pay for it yourself?"

She opened her mouth to object before stopping herself. "This is so unfair," she said finally with a pout.

"Perfect! It's finished!"

Phineas looked proudly at the finished contraption of the day. On top of what was previously described, there was a cube of shining metal dotted with bolts, the underside of which was open.

"All you have to do is stand under it, so your head is in the cube, and the machine will know what makes you happiest and will project it into your thoughts," Phineas clarified.

Buford had arrived off-screen and glanced down at Baljeet. The difference in height was very noticeable. "I see a design flaw here," he pointed out, referring to the presumed unchanging height of the machine.

"Don't worry. It's adjustable—like all the best things are!"

Isabella walked over to it with curiosity and asked, "Can I go first?"

"Of course you can, Isabella."

She ducked underneath and raised her head up to look at the dull flat surface of one of the sides of the cube. Really, the entire machine seemed less dynamic and extravagant than Phineas and Ferb's usual exploits. It had looked positively unnoticeable in their backyard, so small and seemingly insignificant. She briefly wondered if there was something about this day that had caused that difference; then, Isabella figured that she shouldn't try to decipher anything until after she'd used the happiness machine. "So… tell me again what happens?"

Instead of answering, Phineas flicked a switch on the machine.

"Oh, wow," she said in wonder as the sensations began. The machine produced something like a memory or a dream, but it was done in a way that seemed to be completely uncontrolled by the individual and was more visual.

Since only one person could use it at a time, the rest of the group found themselves standing around with nothing to do but observe Isabella's reactions. That might have been a good way to gauge how they'd find using it if only it hadn't been so uninteresting. Isabella was stood still and the machine didn't even have any lights or whirring parts.

It was a tad awkward, in fact. Usually, the things that occurred during the summer were entirely engaging. Whether they'd be on a ride, speaking another language or spending a day on a beach, they'd all be involved and active. Today's activities were strangely stoic.

Baljeet decided to pique up in favour of idle silence. "Can she hear us?" he questioned.

Phineas, unaware of how odd his friends were finding the event of the day, was looking on with a smile on his face that suggested pride in his work. "Yeah, but I don't think she's paying attention."

"I'm certainly paying attention to you, Phineas," Isabella interjected. She always liked to let Phineas know how much he meant to her when the opportunity arose. It might have been partly due to the fact that she hadn't yet been brave enough to confess her feelings for him… She'd get round to it, she told herself.

"That's nice of you, Isabella. It won't be long before it stops," he said, oblivious as ever to that dreamy quality of her voice.

Used to Phineas missing the point, she wasn't disappointed at the uninspiring response. Rather, she was delighted to hear him say that she was nice. The simplest of things he did sent Isabella's senses a-fluttering, and that experience was increased tenfold by the machine's projections of an idyllic future they'd share. "One day…" she said with a dazed look at her childhood love.

Phineas happened to be serendipitously looking at Baljeet as he queried, "Want to go next?"

"Oh, I would very much like to try it," Baljeet responded, eager to do something more interesting than standing around.

"Try away, my friend."

There was another spell of motionless minutes spent dawdling. Isabella was coming down from her fleeting joy to a more quiet contentedness; Buford was watching Baljeet to spy any reactions (difficult, since his face was hidden by the cube of the machine); Ferb was packing up their supplies into the garage; and Phineas stayed oblivious to everything in his watchful attentiveness. After taking his turn, Baljeet distractedly said, "I must go and do some schoolwork," and began to skip away before flinching and walking normally.

"Yeah, that's right, Baljeet. You just walk normally," Buford warned with a menacing expression. Baljeet sped up slightly as he left the backyard, even though he had predicted Buford's disapproval of his unmanliness.

"I guess he was thinking of the good grade he's going to get for it," Phineas commented with a sideways glance towards Ferb, a subtle signal that he was addressing him.

Isabella's eyes widened as a thought entered her mind. "Ah, dang. Phineas, I forgot that my mom wants me home to help clean up. I was only meant to quickly check what you were building, but, well, I guess I get carried away when I'm with you," she confessed with a tilt of her head and fluttering eyelashes.

Phineas nodded slowly. "Have fun," he said, somewhat distracted by a thought that had entered his mind as well. He supposed that not having to supervise things allowed it to jump into his head the way it did—whatever the reason, he realised something about the day.

The point of this day's activity was to cheer Phineas up after being agitated by unpleasant emotions—and those simply no longer seemed like an issue. Of course, he never intended to exclude everyone else from the abilities of his machine, but it was the entire reason he and Ferb built it. So the fact that none of it was needed made him wonder if it'd been a little selfish and impulsive.

He had to remind himself that his friends wouldn't think that of him, and that they probably appreciated the chance to use the machine themselves.

In any case, he figured that now would be a good opportunity to analyse where those emotions were coming from. When he'd been watching the television that morning with Ferb, he hadn't been able to concentrate at all. Now, he was feeling much more clear-headed and able to enjoy what was happening.

So what was different?

Watching the television? He supposed that was just more boring than spending time with his friends. But… no—there were occasional evenings where the family would sit and watch a show together, and he'd been fine during those times.

The time of day? He'd already ruled that variable out; judging from his past experiences, it apparently didn't affect him.

What else could it be?

Lost in his thoughts, he didn't see that Isabella had initially waited for him to say more. With him not forthcoming, she sighed and left a little despondently.

Inwardly reprimanding himself for not being smart enough to figure himself out, he abruptly decided what he'd do. "I'm gonna go next. Switch it on for me, Ferb-meister."

Ferb flicked the switch when the redhead had gotten into position. Buford looked at him in the subsequent silence and figured he'd try to make conversation. "So… what's it like, barely ever changing expressions?"

Ferb stared at him for the following seconds. He wasn't leaving the question unanswered because he had nothing to say; he just didn't feel the need to say it. He'd discovered that people didn't respond badly to his silence, and if they were perfectly fine with it, so was he.

Buford concluded that making conversation with a less than talkative person obviously wasn't very satisfying. Having to reply to nothing, he said: "I see."

In the midst of his friends' one-sided conversation, Phineas was smiling at the images that'd been generated in his mind. He and Ferb were having a friendly tussle, something that Phineas had always found fun, despite barely ever doing. Though the Ferb in his thoughts was enjoying himself, the real Ferb had grown to think of it as uncouth over the years. He saw himself laughing and calming down as he rolled off of the green-haired boy, sitting and resting on the ground. "Don't you love this, Ferb?"

"Actually, I just love you, Phineas."

He couldn't think much more than Wait, what? Because, woah, woah, woah, hold up. Where on earth did that come from? That wasn't something his brother ever said with so much… emotion. It made Phineas get an inexplicably warm feeling in his chest, which translated onto his face as a blush. But, before he could think about what this all meant, he quickly realised that the scene was still unfolding and hastened to turn his attention back to it.

"I love you too, Ferb."

But… this… how could… Phineas' thoughts were a jumble. And he was afraid to say that was partially because of the blissful feeling he was getting at seeing him and Ferb getting closer… and closer…

Well, at least the machine worked.

Phineas moved under and away from it, the images dissipating from his mind just before their lips would've touch, feeling rather troubled. His expression grew worried as he looked at his step-brother. "… I'm just going to go to our room, Ferb," he said unconfidently before running off.

Ferb looked quickly to Buford before following after him.

"That's unusual for them two. I'm gonna try this machine thing anyway."

After using the appliance for a minute or so, Buford said to himself, "Well, that reveals a lot about me." He looked at the machine, then to his right and left, before holstering it onto his shoulder and leaving with it. Considering all Phineas and Ferb's inventions disappeared, he was certain they wouldn't miss it. And if they did—well, he was a bully. He'd say he had obviously meant to make them upset.

Phineas walked quickly into his room and sat on the nearest bed. Thinking about it, that vague, nagging feeling—that was want. He'd realised why it was sometimes stronger or weaker: it always diminished when he was with other people, because during those times, Ferb wasn't the only thing he focused on. But… how hadn't he figured it out before now? When had it even developed? And why?

Phineas was interrupted from his thoughts by Ferb coming into the room. He looked up at him with the same worried expression he'd shown before, so Ferb quickly took a seat besides his brother on the bed and waited patiently for an explanation.

"I… I don't get it, Ferb. I thought I was pretty aware of romance. I understand what happens between Candace and Jeremy, and I knew that when you used to have a crush on that Vanessa girl, her leaving you in Paris was upsetting. We even did a good job of making it when Mishti came to visit, and for our parents' anniversary. So… why, when I'm involved, do I need a machine to reveal its existence? Not that there's—it's not mutual!" He corrected, eyebrows furrowing as he put a hand over his eyes.

There was a short pause. "I wouldn't be so sure of that."

Phineas immediately reacted, hand flying down from his face to clutch the sheets as he looked at Ferb with wide eyes. "What?" he said with quiet fright. "But this isn't—it's not right… is it?" Phineas abruptly sounded very vulnerable.

Ferb looked confused for a moment, but then quoted his brother by saying: "What's not to like about what makes you happy?"

Unable to keep himself from reacting strongly when his emotions were running on overload, Phineas' hands swiftly moved to grab his companion's arm. "When what makes me happy is my supposed brother doing things that aren't brotherly at all! We're not related by blood, but that doesn't excuse me, does it?"

Phineas was asking him so many questions, and in such a flurry of emotion, Ferb thought. It was so unusual for him to be this reliant on Ferb for answers. But it was infinitely more surprising that Phineas had been talking about him, and not about Isabella, as he'd firstly assumed. Romance, mutuality, illicitness and joy… It had revealed a lot.

It had revealed that Phineas actually wanted romance for himself; while he had always been perfectly aware of its existence, as he pointed out, he'd never seemed to connect what he knew about it with himself. Never did he wonder what it'd be like to have a girlfriend, not even when there was so much suggestion of the idea surrounding him. He simply kept his mind occupied on other things. But judging by how the machine seemingly proposed a relationship between him and Ferb, he did have these thoughts, if not entirely consciously. Ferb supposed the distraught came from how the revelation had sneaked up on Phineas without his entire consent; he couldn't think of the why, the when or the how of the thoughts while they all lay in his subconscious. Instead, he had to have these questions thrust upon him suddenly, in the middle of an otherwise ordinary day.

It had also revealed that the snatches of dreams, the short-lived and ignored fantasies Ferb had, weren't worth ignoring.

While Ferb had always been mature, had always been comfortable with his thoughts and feelings, and very aware of them (unlike Phineas), it didn't stop the fact that some of them just couldn't be a part of his life.

He had managed to move past Vanessa: one day, he'd seen her kissing a boy with a purple streak in his hair while his group of friends were at the park. He only felt betrayed until he realised that he had no reason to think that she had betrayed him. With years between the two of them, and not much of a relationship beyond a few days spent together, how could he be offended that she had a boyfriend? Of course, that was making him seem more rational than he was at the time—he'd been beleaguered by cheerless thoughts for days. It had been spending time looking at the maths of blueprints that made him think he shouldn't be ruled by these regrets—instead, he should look at the situation indifferently so as to achieve a more balanced and collected state of mind. Because that was how one viewed equations; no opinions changed the fact that two and two makes four, in the same way that no opinions changed the fact that Vanessa wouldn't be with Ferb.

There was no benefit to feeling heartache; it only pulled him away from his ever-lasting endeavour to make every day count and caused Phineas anguish.

Phineas…

It would appear that Ferb's mind wanted to rebel against the easy, the commonplace, the uncomplicated. Yes, when he had managed to get past his crush on a girl years older than him, growing up caused him to think differently about his step-brother. Being in such close-quarters with Phineas meant that it was extremely easy to spend quiet moments just looking at him, which was when Ferb would realise how fond he was of him, and with the addition of growth, he eventually began imagining having relations with the bright spirit. Nowadays, he knew he was head-over-heels in love with him. With so much adoration infusing their bond on Ferb's side, shown by his utter willingness to spend every moment with Phineas and to produce anything the red-headed's imagination came up with, it was all too easy for the familial love to translate to romantic love.

But he never, ever revealed this was what he felt. He had to ignore the dreams and fantasies he had; this was more impossible and awkward than anything to do with a girl that was six years older than him. Not to mention that, until now, he'd thought that it could only have been him considering it. Why would Phineas think of him as anything but a brother? There was not a smidgeon of evidence that he did.

But this was, apparently, because he didn't realise that was what he wanted. They…they both felt the same way about each other, Ferb thought with hesitance. He'd always had to deny himself that luxury before…

So, finally, the situation revealed that the unacceptable nature of their proposed relationship wasn't stopping either of them from feeling hopelessly and boundlessly delighted by it. It most certainly was wrong; they had the same parents, the same sister and the same household. They called each other 'brother' without a second thought. But this was only a word said without meaning—it had never adequately encompassed the friendship between the two of them. And as for their shared sister and parents? While Phineas and Ferb both felt the same way towards Candace, Linda and Lawrence, these feelings didn't reflect how they felt towards each other; this was a distinctly different and separate issue from anything else to do with their household.

A relationship between the two of them would be incredibly awkward for their family, fraught with difficulties and worries, but this didn't seem to matter in comparison to what they wanted. This machine revealed that becoming Ferb's boyfriend would make Phineas happier than anything; Ferb could surely say this was mutual. He could be there for Phineas in such an enhanced way, as more than just a friend or a brother or a lover.

They were everything to each other.

Phineas thought of Ferb singularly as the most incredibly member of the human race. More than simply having a vast wealth of knowledge, the green-haired boy was able to do the impossible, and this was what drove Phineas to call their shenanigans after him; he dedicated bike races and game tournaments to Ferb in amongst nameless inventions and those dedicated to his dear platypus. Meanwhile, Phineas was Ferb's favourite person in the world: amazing, ever elated, inspiring and enchanting. He never used his abilities for anything but to simply have fun, and Ferb found that incredibly admirable.

With all this in his mind, aiming to calm Phineas' worries, Ferb gently took the hands that held his arm with both of his own, giving the redhead a small smile.

Phineas gazed at their hands for a few moments, firstly with blankness, until his thoughts picked up on Ferb's intended message, and then he looked with wonder. He smiled to himself before turning his eyes to his step-brother. "You feel the same way? See, that makes me even happier than anything the machine came up with, 'cause you're everything to me, Ferb—you're the person I love in every way possible. And, really, you've always been the one to make me happy—you and—oh, there you are, Perry," he interjected, spotting the mammal in the doorway and giving him a bright grin. The platypus chattered at the scene, before he went to attend to something much more important. Namely, having a nap.

Ferb, overcome with affection, enveloped Phineas in a hug, and Phineas revelled in it, holding the green-haired boy closely. "You didn't get to use the machine, Ferb," he remarked.

"I don't need to when I have you."

"Corny," Phineas responded, but he held Ferb tighter because, despite what he said, that really had made his heart soar. Then, that emotion raised a hypothesis. "Maybe—maybe, this isn't right, but we can accept it if it means joy like this," Phineas suggested hesitantly. Ferb was glad to hear Phineas answering things for himself again, and gladder that the answer seemed so right in spite of how wrong the question was.

Because the two would always make the most of every day, and they would always be inseparable. If their relationship changed, so be it. After all, they did truly wonderful things when they were together.

Fade in from black: a scene to accompany the credits.

"Wow, Candace. You look… different." Phineas commented.

"Not. A. Word."

"Doesn't she look nice, boys?" Linda said with a smile.

"I think that hairstyle suits you better, mom."

"I think we both suit it," she countered fairly. "So, how was your day?"

Phineas looked towards Ferb. "It was… really, really good." He beamed. "Happy."

Cue ending music along with the Disney logo.

Cover art is courtesy of the wonderful Ambiefox on deviantART, or ferbfletch on Tumblr.

The title's full quote is "Happiness lies in our own backyard, but it's often well hidden by crabgrass." Pretty suitable, isn't it?