AN: This is "They Say That I Don't Belong, Say That I Should Retreat, That I'm Marching To The Rhythm Of A Lonesome Defeat", title from Battle Symphony by Linkin Park, which is too long to use on this site while keeping the tone, hence the change. Another limitation of this site, compared to ao3, is that I can't actually link the songs at the end, just mention them. The ao3 version has actual links.

This one's a soulmate AU. The "song stuck in your head is what your soulmate's listening to" sort of soulmate, and the "canon never says it's not happening" type of AU. :P

The day they met was otherwise ordinary, yet it changed their lives forever.

Perry tailed his new nemesis, tuning out the ever-present melody thrumming through his head, the one that had never meant anything in the past. Why would that change, just because this evil scientist was humming to himself as he walked? That the sounds matched, the echo in his head and the music in his ears, didn't register.

And yet, not even the practiced mask of professional stoicism could keep him unaware forever.

It started slow. A grudging admiration of the man's obviously well-rehearsed performances. Tapping his feet to the rhythm. And then, to his shock, he found himself paying attention to Heinz's singing voice for the first time.

The same voice that had filled his head with song his whole life.

Since the beginning, Perry the Platypus had known music. Unfamiliar melodies echoed through his mind, filling every waking moment with song, until it was all he could do to keep his fingers still.

It wasn't until he'd been placed with a human family that he'd found out why.

Humans had this concept of soulmates, of an inexplicable connection between people who complete each other in some way, bound together by music. Perry'd think it a fairytale if he weren't living it.

Even then, he decided it wasn't much of a priority for him. So what if he had a soulmate? That didn't change his responsibilities.

And so his life continued as normal.

His mind may have music, but that didn't have to mean anything. After all, everything he needed, he had with his family.

Determined to ignore the newfound knowledge that promised to change all his relationships forever, Perry continued on as he always had, stony impassiveness on his face whenever his nemesis would sing. After all, he was nothing if not a professional.

And yet, had Heinz looked, he would have seen the subtle twitch of fingers and tap of feet Perry could no longer suppress.

Perry supposed he should be thankful his nemesis had never learned to listen. Whatever past the man had, the pain pouring out bit by bit, day by day, it was clear Heinz had been left with a desperate need to be heard. By anyone.

And who better than a patient soul?

What a pair they made. A platypus who'd never needed to speak and an ocelot who'd never had the chance.

The thing about soulmates is, the connection goes both ways.

Where Perry's life had filled with music, so too did Heinz's, just at the edge of his consciousness. And yet, the habit of a lifetime was hard to break.

Every moment of his life had been surrounded in song, by choice. He no longer heard the silence, the empty space where music should have been, because he'd long since filled it with his voice and his deft fingers dancing over every instrument that came to hand and an outpouring of emotion he couldn't express any other way.

And yet, the absence he'd almost grown used to still ached, late at night when he couldn't escape it.

In the face of that, it was no wonder he didn't hear the quiet hum in his soul.

Since the beginning, Heinz Doofenshmirtz had known silence. The silence of the forest, the silence of the night, the silence in his head.

He'd thought it normal at first. After all, what prey would risk the waiting hunters? One misplaced foot, one snapped twig, and a hapless mouse would alert every nearby predator to their soon-to-be-ended existence. Silence was a boon for an ocelot.

It was different for humans. He'd learned that the hard way, between the pitying glances whenever he dared admit the silence and the "lighthearted" "teasing" that left him confused and hurting. Here, too, he's different. (Wrong.)

And so he sang.

If he truly had no soulmate, like everyone claimed, he'd make his own music. His mind may have been silent, but his life wouldn't be. Of that, he'd make sure.

Realisation crept up on him slowly.

The echoes of his musical numbers while he strutted on stage, he could ignore, telling himself it was merely a side-effect of his years of practice. The echoes while he lay in bed trying to sleep, not so much.

The next day, he paused mid-monologue to yawn. "Sorry, Perry the Platypus, I didn't get much sleep last night." Then, "Your Organisation records everything, don't they?" he said, hesitant.

Perry nodded, unsure where his nemesis was going.

"Including my musical numbers?" Another nod. "Is there a, you know, list of people with access?"

Technically all of OWCA, Perry knew. But he'd known his nemesis long enough to hear what the man was really asking.

Who's my soulmate?

Climbing out of the usual trap, he took Heinz's hands.

I am.

It didn't fix everything, not immediately. But as their lives changed around them, in ways neither of them had expected, they both sought comfort in the connection.

Leading them both to a night at Danville's local karaoke bar.

After an heartfelt rendition of What Is This Feeling? (complete with the chorus girls Heinz had hired), a well-choreographed spectacle of You're The One That I Want (one said backup dancers had practiced for weeks in preparation), and an impassioned performance of Rival Destinies (where the chorus girls took a well-deserved rest), they stood facing each other, microphones clutched in hand and paw, panting in exhilaration.

"One more, Perry the Platypus?" Heinz asked, unable to help his grin. He had a soulmate. Not once in his long life had he expected this at all, let alone how it would feel to be so perfectly in sync with someone.

Perry, a matching grin on his face, nodded. On his part, he'd always found teamwork, of any sort, difficult, until the day his nemesis had literally stumbled into his world, so different from him and yet perfectly matched to the rhythms in his heart. Side by side with his nemesis, this understanding, this connection, seemed almost effortless.

Drums rolled, the opening to a song they both knew as intimately as a punch to the face. Hand found paw, and paw found hand, neither of them needing to look to find each other.

Sauntering to the front of the stage, Perry lifted the microphone to his bill, gaze roaming over the breathless crowd.

"I'm a semiaquatic egg-laying mammal of action," he sang, voice ringing out in a clear countertenor, the perfect complement to Heinz's rough tenor as the man joined in on the next line. Their voices blending, they poured heart and soul into their performance, eyes only for one another. The world dropped away, but for the backup dancers who rejoined them at the chorus, linking arms for Heinz's now-customary kickline.

This was all they needed. A handful of chorus girls, a familiar melody...

...and a partner, nemesis, soulmate, to make their hearts sing.

AN: I will keep uploading whether or not anyone leaves a review, don't you worry ;)