Heyo! ROTTMNT has claimed my soul for the time being. To my fellow OKKO fans, OKKO is still my main fandom, and I'm still writing the Perfect AU fics, and have upcoming ideas in mind. I'm sick though, and not feeling up to writing out those last handfuls of paragraphs on the current story. So instead, I wrote a short TMNT fic that I didn't care if it was any good. But it's up to you readers to determine how it is.

Aside from being sick, please note that I've been in this fandom for all of two or three weeks, so I probably have the characterization a bit off. Also, it's past midnight. So if you see any blatant errors, please let me know! :D

Life can be pretty interesting when you're a mutant. It's more interesting being a mutant turtle who lives in the sewers with your three brothers and rat father, and even more so when said brothers aren't even the same kind of turtle. Life definitely wasn't boring, especially if you were arguably the most interesting out of all of them. Which isn't to say that everyone else didn't have their oddities.

Raphael had a vermiform. Nobody knew the word for the thing on the end of Raph's tongue until Donnie informed them, but whatever it was, it was a topic of much interest in their youngest years. It wasn't entirely uncommon to see the turtles huddled around their eldest brother, encouraging him to make the wormlike appendage wiggle in silly ways, and giggling madly when he did. Raph didn't particularly enjoy the attention, but it made his brothers happy, and he was never one to let them down.

Leonardo had the strange habit of wiggling his digits when he was upset. It wasn't a common sight, but it was one his siblings had grown familiar with nonetheless. Petty squabbles were a frequent occurrence, usually with Mikey or Donnie. As annoying as they could be, they rarely got on Leo's nerves. But there were times where someone managed to rub him in precisely the wrong way, and then his fingers would start shaking, then fluttering. On a good day, the perpetrator would run crying to Splinter, covered in ugly bruises and bite marks that would need immediate treatment, possibly nursing a broken toe or finger. Lou forbid anyone incur his wrath on a bad day.

Michelangelo was remarkably resistant to foodborne illnesses. One time when the turtles were barely old enough to explore the nearby tunnels on their own, they had come across some sort of fungus. Mikey, being only four, had immediately stuffed an entire handful in his mouth. He had nearly scared the shells off of his brothers, but when he didn't start frothing at the mouth and convulsing, they assumed it was safe and tried it as well. Splinter was treating them for fungi poisoning hours later, but Mikey was perfectly fine, even after days had passed. To this day, he could still be seen snacking on the fungus, even sprinkling it on pizza.

And Donatello...

Nobody could figure out what Donnie's "quirk" was. They all knew about his soft shell, but that wasn't particularly strange. No, it had to be something else; the question was what.

It wasn't until their preteens, Raph being the oldest at 11, that they found out. During one of their routine sewer expeditions, they had come across a large dip in their path, the ground sinking either due to age and deterioration, or due to the constantly trickling water overhead eroding the surface. Either way, it wasn't too deep, maybe three feet tops.

"Cool, a swimming pool!" cheered Mikey, already jogging backwards in preparation to jump in.

However, Raph held him back, grabbing him by the lip of his shell behind his neck. "Now hold on," he said. "We don't even know if the water's safe."

"Seems pretty safe to me," Leo called, already in the makeshift pool. His entire lower half was submerged, his upper half supported by him leaning back on his elbows at the edge of the water.

Raph nearly had a conniption at that. "Leo, what are you doing?! What if there's something in the water?! Like, I dunno, leeches?!"

"There are no leeches," Donnie scoffed, leaning in close to inspect the water as his goggles zoomed in and out seemingly at random. "It's an isolated body of water. The worst you're going to find in here is algae, maybe mosquito larvae. But it isn't the right time of year for those things, so..."

Raph still looked uncertain, but before he could say anything more, Mikey wriggled out of his grip, cackling happily as he threw himself into the water with an undignified belly flop. Raph let out a heavy sigh, one hand running down his face. His brothers could be such a handful. But the ground didn't collapse under them, and they didn't get eaten alive by piranhas, so no harm no foul, he supposed.

Within minutes, the turtles had themselves situated in the pool. Mikey, of course, was swimming laps, the water not deep, but plenty wide enough to accommodate him. He would occasionally splash his brothers in passing, sometimes but not always intentionally. Leo lounged at the edge for a while, but would here and there dive in and race his youngest brother, only to return to relaxing. Raph had finally decided to brave the water, and had found himself napping in the center, fully submerged with only his shell spikes protruding. He stayed under for minutes at a time, only coming up to take a breath of fresh air before diving again. Donnie didn't go into the water at all, instead sitting nearby to type away at the display coiled around his arm, occasionally dipping his finger in and studying the rivulets that ran down.

Leo, clearly, wasn't happy with this. "Hey Donnie, why don't you join us? The water's great!"

"Not interested," Donnie replied, not even looking up. "I don't have my waterproof gear anyway."

"Then just take your stuff off so it doesn't get wet," Leo told him like it was the most obvious thing in the world.

Donnie did look up at that, pained reluctance clear on his face. He never went anywhere without at least one invention; he felt naked without them, and his brothers knew this. "But I..."

"C'mon, Don!" Mikey called, poking his head through the surface. "It's so much fun in here! Nobody wants you to miss out!"

The purple turtle considered his words for a while, stiff with reluctance, but after a time, he sighed. "Ugh, fine. But only because I know I won't hear the end of it otherwise."

The first thing Donnie removed was his goggles, slipping them off of his forehead and carefully setting them down a safe distance from the water. Then came his wrist display, detaching from his arm with a quiet hiss and joining the goggles.

Then, finally, came the battle shell. It was still in its early stages of development, mostly consisting of a hunk of metal and two inaccurate protruding arms. Still, despite its lack of functionality, Donnie insisted on wearing it everywhere he went, pointedly ignoring any worry his brothers may have expressed. They could still see faint scratches on his soft shell from previous failures, only now healing over.

But they knew better than to stare.

It was almost a relief when their middle brother finally dove into the water, obscuring the tiny scars from view.

"See? It feels nice, doesn't it?" Mikey asked, beaming at Donnie.

The purple turtle lifted the head, his chin still mostly submerged. His expression remained neutral, even as his eyebrows twitched as he fought off an eyeroll. "Okay, yes Michael, the water is somewhat pleasant." Mikey squealed in delight, ensnaring his older brother in a short hug.

After that, the turtles largely continued their own activities. Although, Leo and Mikey had both taken to simply basking, worn out from their earlier racing. Raph continued napping, completely unaware of his immediate younger bro's brief plight.

That was, until Leo noticed something amiss.

"Uh, guys?" he hummed. "Does anybody know where Donnie went?"

"He probably left," Raph replied, having just come up for air. "You guys know him. You can't keep him out of his lab for long."

"But I never saw him get up," Mikey argued, "and I've been up here this whole time!"

"So that would mean..." Raph started.

"...that he's still in the water," Leo finished, eyebrows knit with concern. "Has anybody even seen him come up?"

"I haven't," Mikey moaned, the last syllable coming out as a nervous squeak. "He can't hold his breath that long, can he, guys?"

"DONNIE!" Raph shouted in alarm, quickly jumping to his feet. His brothers immediately followed suit, and all three began wading through the pool in search of their favorite genius.

"Where did you go, Donnie?!" Mikey called. "DONNIE!"

"I found him!" Leo announced, frantically pointing at a dark spot in the water that could definitely be the turtle they were looking for. "What are you supposed to do in these situations?! Do we move him?! Leave him in?! Ugh, I am NOT giving him mouth-to-mouth!"

"Okay, nobody panic!" Raph told them, even though it was clear as day on his own face, hands waving wildly in front of his chest. "We gotta think about this calmly and rationally. Maybe if we... uh..."

"Donnie is the calm and rational one, Raph!" Leo wailed, vigorously shaking the snapping turtle.

"I know, I know, but if we just-"

"Oh mi gosh, we killed Donnie!" Mikey cried, tears and snot spilling down his face. "What do we do?! Pops never trained us to un-drown somebody!"

"What are you guys going on about now?" Donnie asked in a deadpan drone.

All three of his brothers froze, heads snapping in his direction. They gaped at him like goldfish for a long time, and he quirked one muddled brow, awaiting an answer. It was Leo who finally broke the silence. "...Uh, Don...?"

"What?"

Donnie's head had completely broken the surface, and with it way more neck than any of them were used to seeing. At least a handful of inches more, in fact.

"...Has your neck always been that long?"

Raph ducked his head under, resurfacing seconds later with a look of utter shock on his face. "His body is touching the bottom. Like, his chest and everything."

"No way!" Mikey gasped, taking a look for himself. "I didn't know you COULD have a neck like that! Unless you were a giraffe, but you're a turtle, like us!"

Donnie frowned, his head lowering enough to obscure his neck. "It's not a big deal or anything. I've always been able to do that."

"Then how come we've never seen it?" Leo challenged.

"Because I knew this would happen," Donnie grumbled.

"C'mon, we don't mean nothing by it," Raph cooed, elbowing the slider even as he tried to reassure Donnie. "It's just... surprising, is all."

"Can I see it over the water?!" Mikey asked enthusiastically, eyes sparkling.

Donnie, however, had decided that he was done with the gawking. He lifted himself to his full height, his neck slowly collapsing as he did, as if it hadn't just stretched by three feet. He stormed over to his gear, gathering his things and leaving his brothers to their own devices.

The three were silent for a moment, their jovial moods soured. "Great, he's got another soft spot," Leo muttered, both of his brothers slugging him in the arm for his quip.

A week later, Donnie had added shoulder braces to his shell, firmly pressed against either side of his own neck. Nobody questioned him about the addition, and that was just as well. It was better not to upset the one turtle who could put Leo's famous rages to shame.

Here you go! Enjoy my fairly needless headcanons. :P I mean, have you guys ever seen a soft-shell turtle's neck? Those things get long! Supposedly it's to breathe when hunting at the bottom of the water, which is aided by an inefficient underwater breathing mechanism. So if you're wondering how Donnie stayed under long enough to be worrying, that's why. He can breathe down there as long as he stays still, according to biology and according to me. The rest of the quirky stuff is true too, though I took a little liberty with Mikey. Box turtles sometimes eat poisonous mushrooms. I guess they have some immunity to the toxins, but I do know that it taints their meat. Maybe a defensive thing, I dunno. I'm turtle-dumb.

So, I hope you guys enjoyed this! Feel free to give me pointers on what I could improve. Not mandatory, but I would really appreciate it! :D