Work Text:
How does one naturally bring up a person making themselves their own test subject, especially when one has merely glimpsed its occurance once and has no idea how often it actually happens?
Leo doesn't know, and it's been bothering him for weeks.
When he first realized that, yeah, his own brother poured a random chemical on himself to test a theory (hypothesis, he can hear Donnie say), he kind of had more urgent issues to handle. Firstly, processing the fact that Donnie had just created more-or-less a cure for mutation was a bit of a challenge. It was something Leo had thought about as a kid often, especially with how the others talked on the subject constantly, but now it made his stomach turn. He was a ninja turtle, and he didn't want to be anyone else--even if it made living in New York easier.
But his brothers clearly didn't think the same, which brought Leo to issue number-two: keeping this recent development a secret. He knew that, while Donnie could handle his idea being rejected, Mikey and Raph wouldn't be able to let it go. So Leo tried to hide the newfound information--to no avail. Then he had to deal with the fallout, go to Brazil to fight the Foot, come back from Brazil to fight the Kraang, reveal his family to a bunch of trigger-happy New York cops, and help clean up his city. There was just no time to stop and rip into Donnie about why he would ever pour such a substance on his skin so willingly, so thoughtlessly. (Except it wasn't thoughtless; in fact, it was measured thoroughly, planned meticulously, because Leo knows Donnie works no other way. He can't tell if this information makes him feel better or worse.)
But now that New York has begun to settle back down, Leo keeps Donnie company in his lab a little longer. Asks a few more questions about his experiments. He doesn't always understand what his younger brother says, so he presses for more clarification. Nothing screams Donnie uses himself as the science-version of a training dummy to Leo, but there are small holes in the explanations that leave him a little concerned. Leo doesn't want to make it a big deal if it isn't, but he doesn't want to misjudge the situation for being better than it actually is. He tries to be patient with his assessment. He tries to be less pushy, less demanding, less forceful in and out of combat. It's an uphill battle, but he's determined.
"So how do we know our medical supplies will work in the first place?" Leo asks one day, watching him synthesize their equivalent of acetaminophen. Donnie flat-out refuses to steal from surface medical centers, and even if he didn't, Leo wouldn't let him. So he learns to create his own remedies for their problems.
"Oh," Donnie begins with surprise, still getting used to the sudden interest in his work, "well, considering the fact that we aren't biologically one species or the other, like most creatures are, medicine made for humans or turtles respectively won't do much for us. Mostly, they'd cancel out or make our conditions worse. So, I essentially had to figure out a balance between the terrapin and homosapien in our genetics, and then I modeled the medicines based off of what is known about both species. It took some trial-and-error, but," he shrugs, using an eyedrop to finish the formula, "was worth it."
That comment sends a few alarm bells ringing in Leo's mind. He echoes, "Trial and error?"
Donnie glances at him, "Well, yeah. There isn't exactly a book on how to treat people like us effectively, you know. A lot of the first few formulas I had drafted up practically made zero changes during the testing stages--while others produced less than desirable outcomes. I've created better formulas since then, though, so don't worry."
Leo can tell; for all of their intense migraines, exhausted muscles, medical emergencies, and sleepless nights, Donnie's remedies have been an aide. They really should thank him more often.
What Leo can't tell, however, is if these tests were conducted in a.. healthy way. And his hard-earned patience runs a little thinner at the way Donnie's explanations dance around the finer details casually, effortlessly, like he's trained himself to keep certain secrets no matter how distracted he may get the same way he's been trained to dodge hits automatically by Splinter.
"Don," Leo starts again, searching for more fitting words, the right way to pull Donnie out of his shell, "how do you test it?"
His brother pauses, caught off-guard, "Huh? Test what?"
"Anything," Leo answers immediately. "All of it. How do you test your formulas? Who do you test it on? Is there some tiny box turtle you've got hidden around here that I should be worried about?" He tries for a joke, but the way Donnie stares blankly in response sours the taste of humor on his tongue.
Donnie says, with the most matter-of-fact voice, "Uh, why would we need another turtle, especially an un-mutated one? There's four of us right here."
Such a simple, obvious answer. Like it's honestly the very first thought that crosses Donnie's mind whenever he's asked that question. The unbothered, casual tone of voice he uses when he so easily implies that they could be (and have been) test subjects--it strikes Leo right in the gut.
"Are you telling me," Leo begins again, blood beginning to heat up, "that you've been using us and yourself as- as lab rats all this time?"
Donnie looks offended, "Lab- don't say that kind of stuff, Leo, Splinter's our dad." Before Leo can become upset and ask why that was the part that he latched onto, his brother continues. "And no, I haven't done any kind of uninformed testing on you. Geez, Leo, have a little more faith in me. I typically use my DNA."
"Just your DNA?" Leo presses.
Donnie falters, "I- technically, not just, Leo. It takes more than a sample of DNA to make sure something is completely safe, especially when it comes to people like us."
Leo doesn't understand what Donnie's not getting about how messed up that is. He asks, "Well, can't you just- I don't know, study the effects under a microscope? Without injecting random crap into your body?"
Donnie frowns, rounding the table to grab a missing tool. "I mean.. no. You can't test these complicated processes on just a slide of cells. You have to account for reactions throughout the entire organism, otherwise you're putting a hell of a lot on chance-"
"Otherwise?" Leo repeats, hand gripping the lip of the countertop tighter, "No, no. There is no otherwise, Don, because you are putting a hell of a lot on chance just by testing these things on yourself."
Something shifts in Donnie's face, his frown deepening, his expression hardening. "Jesus, Leo, it's not that big of a-"
"Don't even finish that, Donnie," Leo shuts him down, bubbles rising from his upside-down stomach to creep up his clogged throat. "because you know it isn't true. You, of all people, know exactly how risky this is. You wanna know why I don't believe you? When you say it's not a big deal?"
Donnie glares from across the table. "Enlighten me."
Leo holds the eye contact. "What if I told you to test it on me?"
"..What?"
"You heard me," Leo states steadily, determined and worried and mad, all emotions jumbled in his stomach, knotted in his chest. "What would you say if I told you that, next time you need to test a formula, you should test it on me? If it was an order? How would you feel about that, Don?"
Donnie looks cornered. Conflicted. Like the concept hadn't crossed his mind even once. "I- but- you wouldn't even-"
"Hey," Raph interrupts, grabbing Leo and Donnie's attention in an instant. He grumbles as he enters the room, "The hell's going on in here? Keep this up, and Sensei might hear you."
"Nothing's going on, Raph," Donnie says pointedly.
Leo sets his jaw, eyes dead-set on Donnie. "Yes, actually. You wanna know what's going on? Donnie here decided he deserved to become his own personal test subject. Tell him, Dee. Tell him how you got sick or hurt by experimenting on yourself."
Raph's eyes widen a fraction, pure disbelief as dots start to connect. "So, that week you spent sick outta your mind, leavin' all of us scrambling to get you back to normal, was all because you did what?"
Donnie does wilt a little at that, but he tries to defend himself anyway. "And since then, we haven't gotten a bad flu even once! I call that a win, and I don't see why I shouldn't."
"You don't-" Leo growls, frustrated and desperate to get his point across to his stupid, genius brother. "You're supposed to be smart enough to realize why I'm making this such a big deal. But this? This is done, Donnie. You've got your formulas perfected, and now it's done."
Donnie snaps back, frustration and embarrassment fueling his fire, "And what if something new happens? Something I haven't even accounted for yet, like a super-virus? Mutated bacteria? Parasites? What are we going to do then, Leo?"
"Not this," Leo shakes his head, willing the growing pressure behind his eyes to dissipate. "My god, Donnie, we will figure something out, but the solution will not be this."
"Are you serious?! That's your plan?!" Donnie snaps incredulously. "Great idea, 'Nardo, let's just wing it, sounds perfectly safe-"
"-a lot safer than you using yourself as a-"
"-easonable thing to do, why wouldn't-"
"-no, you know what, I'm about this close t-"
"Alright, both of you need to shut up, and someone needs to go take a walk." Leo and Donnie whip their heads to look at Raph, who's grown irritated by watching the exchange from the sidelines. He glances between the two. "You heard me. Go. Sit in another room. Meditate or some shit. Whatever you gotta do, go do it before someone gets hurt. Now."
The brothers can count almost on one hand the amount of times Donnie's been truly angry--yelling or frustrated beyond words, trembling with rage, unable to take or release a breath. He's too level-headed to let most issues turn him into such a careless agent of anger; hell, he keeps his cool better than all three of his brothers on most days.
Stunned into silence by the turn of events, humiliated and frustrated, Donnie holds his breath and walks out, biting his tongue so hard it bleeds bitter copper onto his tastebuds. Leo starts after him, concern and anger and guilt lacing his features, but Raph stops him with a hand. "Hey, I meant it when I said you two need some time apart now. Give him some room."
Leo turns and paces the lab floor, pent-up and fuming, "I cannot seriously be the only one who's upset by this. Did you hear a word that I said? That he said? God, it's like he thinks his health means absolutely nothing-"
"Leo." Raph cuts in loudly. His brother closes his mouth. He continues, "I'm totally fucking pissed right now. I'm so angry I don't think I'm gonna be able to go to sleep tonight. But teamin' up against him wouldn't have solved anything, not when he's that defensive about it. Trust me, it wouldn't have helped if I was in his position. He needs to cool off before anything we say is gonna get through to him. And to be honest, so do you."
Leo sighs heavily, reigning himself in. It takes a moment, but he manages to say, "You're right."
"'Course I am," Raph shoots back breezily. He starts collecting equipment from Donnie's abandoned project as he calls out, "Hey, Mike. You wanna come in here a sec?"
Silence. Mikey slowly steps into the room like it's booby-trapped. "What's up, fellas?" He greets his brothers sheepishly, drawing out the words in a high-pitched voice. "Totally cool night to be chilling on this side of the sewer, amirite?"
Raph rolls his eyes, "Alright, knucklehead, can you help Leo put this shit up? We know Donnie doesn't like to leave his stuff laying around when he's gone, and I'm assuming the lab is gonna be off-limits for the night." A short glance in Leo's direction assures him that this definitely will be the case.
Mikey steps up immediately, taking the items from Raph's hands as he says confidently, "Totally, brah. We'll get this baby clean in no time." He turns to set the equipment into its proper place before immediately blanking, admitting, "I have no idea what I'm doing."
Leo shakes his head, more amused than he's willing to admit. Raph looks unimpressed as he offers, "Check his little recipe book or somethin' so you don't end up blowing this place to hell." Leo pulls the binder from a hidden compartment in a cupboard, having remembered the placement from watching Donnie at work for hours on end. Raph nods, satisfied, and says, "Now that's settled, I'm gonna go talk Donnie down a bit. I'll be back soon."
Leo gives an affirmative, and Mikey gasps, "Woah, dude, you're acting like.. responsible for the team and stuff." His expression saddens a tad as he comments, "That fight must've been really bad then, huh?"
Leo frowns, clearly agreeing with the sentiment. Raph shrugs it off, keeping his cool as he says, "Eh, I figured I'd give 'em a hand this time. Not too bad for the hothead, though, huh?"
"Don't get a big shell about it, Raph," Leo warns, a smile finally tugging at his face, "Just- make sure he's okay?"
Raph holds out his fist; an invitation. Leo accepts it, bumping their hands together. Raph grins, "You're the boss."
---
Donnie thanks every deity he could ever acknowledge that it's night time when the argument happens--that way, when he hauls himself out of the manhole in a storm of angry muttering, he doesn't worry about running into unsuspecting citizens.
Usually when he's upset, Donnie spends some time in his lab, doing the menial, repetitive tasks to calm his mind. Usually. Considering the fact that his lab has been commandeered--as silly as it is, it's true--for the time being, he'll have to make due. So he skips around various buildings for a while, dodging the adults and teenagers alike who find solace sitting on top of their city in the dead of night.
Fifteen minutes into his 'walk', Donnie spots a gaggle of humans having a celebration on a nearby Brooklyn rooftop. They're playing one of Mikey's favorite songs on the speaker, he realizes with some surprise. He watches from afar, settling close to the ledge of the structure he's claimed.
It's a peaceful thirty minutes of observing their dynamics, absorbing their laughter when it bounces off the walls, smiling when they dance, wincing when they trip, feeling lighter than air when they simply laugh it off and pick themselves up again. Moments like these remind Donnie how much he loves his city, his family--even when he can't show his face to the average New Yorker and his brothers tick him off to no end.
Donnie then sighs because no matter how distracted he may be, he's a trained ninja first and foremost, so he hears his brother's approach before he ever sees it. Raph's voice calls from behind, "Mind if I join you?"
Donnie thinks at least it's not Leo and shakes his head.
Raph sits next to him and says, "Good, 'cause I was kinda planning on stickin' around here anyways." Donnie almost laughs at that, but it only comes out as a short huff. They watch the humans spin around each other lazily, effortlessly, without a care in the world. Raph asks, "Figure out which one's which yet?"
It's a game they play sometimes--purely speculation, but it passes the time and bridges the gap between turtles and humans, if only for a moment. Donnie indulges his older brother's antics, pointing to each person in turn, "My best guess is they're the school teacher, maybe a nurse? I know they crotchet on the side. That one's studying to be a linguistic analyst; she's been excited about her doctorate all night. Those three are retail workers who messed up scheduling their vacations at the same time--they're pissed. That group has been dancing on and off, but that group is clearly in charge of food at every outing." He shifts his focus to the beautiful woman, twirling beneath her wife's guidance. Admiration for her dedication to her craft thrums in his chest. "She's been the heart of the dance-floor. I don't think she even knows how to stop."
Raph grunts, thoughtful, "Yeah, she sure knows what she's doing. But I bet she's gotta sit down sometimes. Y'know?"
Donnie has to laugh that time. At least Leo was trying to be subtle--until he wasn't. He plays innocent, thinking aloud, "Gee, I wonder what that's supposed to mean."
"I have a feeling you get it," Raph muses, sharp eyes on his brother. It's.. easier, this way. Outside of the lab, side-by-side yet not facing each other. Less angry arguments in cold, damp corners and more music and laughter from bright, open rooftops.
"The lack of yelling is a nice change of pace," Donnie comments after a beat.
"Don't get me wrong; I'm also pissed at you," Raph corrects him, that ever-lasting anger staining his tone. "But you're my brother, and as much as I wanna yell my head off about how much you just scared me back there, I'm not riskin' pushing you away. Not after that."
Donnie can't find the right words to articulate a response, so he nods and scoots a little closer to his brother.
He asks hesitantly, "do- at least you understand why I do what I do, right?"
"No, I don't," Raph says honestly, "I don't get it at all. I can't understand why you'd do somethin' like that, 'specially without letting us know 'bout it. I don't know how long you've been going at this, and I'm not sure I wanna know."
Donnie frowns, the heaviness in his chest returning, "You think you might start yelling if you don't like the answer?"
Raph nods, "Damn right."
"So what do you suppose I should do, then?" Donnie asks, desperation creeping into his tone. "Because I don't even know; I mean, just about all of our remedies were perfected that way. How am I going to figure something else out?"
"We," Raph corrects automatically, like the thought of his brother alone carrying the weight of the consequences is purely unthinkable. "And I'm thinkin' that, until something bad happens like you were talking about earlier, you don't go messin' with stuff that ain't a problem yet. If you need to test somethin' like you have been, just- I don't know, tell someone about it? Or let one of us volunteer? 'Cause I dunno about you, but I don't think the only genius scientist we know should risk puttin' himself outta commission during one of his experiments."
Donnie hadn't ever worried about that, he realizes. He'd always known that no matter the unexpected results of his tests, no matter the consequences: "I know you guys have my back."
Raph stares at him, their town's lights reflecting in his eyes, "Yeah, we got your back, D. Always." He bumps Donnie's arm affectionately, and Donnie knocks into his in return. Just a rooftop away, the dancing woman falters in her heels, but her lover and her friends pick her off the floor, and they all laugh warmly into the chilly night air.