It was awkward. It was really, really awkward. Donnie was sat at his desk in his laboratory, fiddling with a set of blueprints he couldn't focus on, while Casey slouched against the wall with a heavy frown on his face.

"This is dumb," he muttered, scuffing his shoes against the floor.

Donnie pinched the blueprints hard, crinkling them. Taking a deep breath, he lay them out on the table. "It wasn't my idea. April asked us to."

Casey threw his arms wide in frustration and accidentally knocked something off a shelf. "So we're just gonna do it? Because she said to?"

The turtle shrugged. "What else can we do?"

"Say no?" The hockey player paled. "Unless- you don't want to, right?"

"What? No!" A maroon blush rose on his emerald cheeks. "O-of course I don't want to! D-do… Do you, or…?"

"No," he replied immediately, folding his arms over his chest. Donnie nodded, his lips pursed.

When April told them she had made a decision, they'd both thought it was over. So when she propositioned them for a threesome? It was a shock. Casey had refused straightaway, his face flaming red, but Donnie had been speechless. When she told them she couldn't give either of them up for the other, that she wanted to have them together or not at all, both of them had wavered.

"We…" Casey huffed. "We can… ugh. We can try, if you want. If it's what she wants."

There was a weird feeling spreading in Donnie's chest. He tried to rub it out as he asked, "Are you sure?"

Casey hesitated, but nodded. "Nothing below the belt though, okay? I don't wanna see any of your turtle junk."

Donnie nodded, feeling relieved. Other than April – who had only seen it briefly in the few times they had coupled – nobody had ever seen his 'turtle junk' before, and he wasn't particularly eager to show it off.

He stood up clumsily, tripping over the chair in his haste to seem casual. Casey snorted, arms dropping to hang at his sides. As Donnie shuffled over, they raised as if to embrace him, then seemed to rethink it and fall again. Donnie didn't stop moving until he was close enough for the tip of Casey's nose to brush his snout.

Then, he tilted his head forward. Casey's lips were softer than his, although even more chapped, and his mouth was about half the size of Donnie's at best. Leaning forward with no anchor was weird, so Donnie gripped Casey's shoulders, pulling him closer and immediately realising this was weirder. He tried to poke his tongue inside and Casey snapped his head away.

"Dude, what're you doing?!" He exclaimed, wiping his mouth. "What's with the tongue?"

Donnie felt his face flush again. "I don't know! That's how I kiss April!"

"I'm not April, man!" Casey reminded him. "And you're doing it wrong anyway, you're not meant to just stick your whole tongue down her throat."

"That's not what I was doing!"

"Yes it was! Look, this is what you did-" Casey pulled Donnie in by his plastron and jammed his tongue into his mouth rather haphazardly, withdrawing it to continue, "-and this is what you're supposed to do."

This time, his tongue slid in slowly and carefully, caressing Donnie's own before beginning to explore his mouth. Without thinking, he closed his eyes, fingers curling tighter around Donnie's shell. Donnie's own hands crept onto the human's waist as his tongue began to roam, too. It was only when Donnie let out a low moan that Casey seemed to realise what they were doing.

"Fuck!" He shoved the turtle away, gasping for breath. "What the hell?! I- You- Why did you…" Wide-eyed, he prodded an accusing finger into his plastron. "Did- Did you like that?"

"Yeah," answered Donnie honestly. Three thick fingers drifted down Casey's body, landing on the hard bulge at the front of his jeans. "And I think you did, too."

Casey's breath caught again as Donnie stroked his growing erection, his touch gentle but firm. When he popped open the button and began to ease the zipper down, Casey didn't stop him. Instead, he groaned. "Fucking April…"

Donnie hummed in agreement, his eyes focused on the grey boxers he was revealing. "That is what got us here. So," his hand paused, his gaze darting up to meet Casey's, "what do you want to do now?"

"I… I don't know," he huffed. "We – We can't just have sex!"

"Well…" Donnie smiled slyly. "April did ask us to get more comfortable with each-other…"

Casey swallowed heavily. "Yeah, I guess she did."

Carefully, Donnie began to tug Casey's jeans down, running one digit over the outside of his boxers as he did so. Casey reached a shaky hand down and freed his now-solid erection from its confines. Donnie glanced over it with his 'science face' on, admiring the throbbing vein on its underside and the way it reddened at the head.

Then a wide tongue shot out, gliding over the cock before it and drawing it into a warm mouth. Casey let out a sound that was either a moan or a shriek, bracing himself against the wall. Donnie sucked diligently, only ever easing up to take him in deeper, one hand reaching between his own legs to fondle his tail. When Casey began to thrust forward, cupping the back of Donnie's head to hold him in place, the turtle released him.

Before Casey had a chance to question him, Donnie had released his tail, his own member dropping down. His was significantly larger and thicker, with a strange sheen over it. Casey reached out to grab it, to torture Donnie as the turtle had done to him, but the moisture on his fingers gave him pause.

"Why is it so… wet?" He asked, squishing his sticky fingers together.

Donnie bit his lip, shrugging shyly. "Turtle penises self-lubricate."

Casey wrinkled his nose. "That's kinda gross."

He chuckled, rubbing his own member to full hardness. "You'll be grateful in a minute."

The turtle spun him around, yanking his jeans and boxers down to his knees as he did so. Casey gripped the edge of the desk for support as Donnie coated one of his fingers with the strange substance, searching the firm ass in front of him for the puckered entrance. When he found it, Donnie let the tip of his finger poke inside first, easing himself in. It was hot and tight and he groaned, his own hard-on throbbing painfully. He rubbed patterns into the walls of the hole, stretching it slowly, as Casey came apart at his touch.

Satisfied the preparation was sufficient, Donnie removed his finger. It earned him a frustrated groan that made his cock twitch. He pulled Casey's cheeks apart and hastily moved himself into place, filling the hole in one strong thrust. Casey howled, digging his nails into the poor table as Donnie shakily seized the human's hips. It was tighter than he had imagined, his member barely fitting inside, and so impossibly hot he thought it might melt him.

First, his thrusts were slow and careful, shifting and stretching inside the hole. Then he began to speed up, his thick fingers carving into Casey's hips, until he could feel himself slamming into the man's prostrate and turning them both to jelly. Casey's nerves were on fire, his body struggling to cope with the sensations, but he ground himself against the cock nonetheless. His hole began to tighten around Donnie, but the turtle continued his frantic pace.

The pressure in Donnie's groin increased. He pressed Casey further into the table, his plastron crushing down on his t-shirt, as he pounded into him. Casey was crying out nonsensically, smacking one fist against the surface in time with the turtle's thrusts. Donnie was grunting with the effort, but he refused to let up.

Casey came first, letting out a scream and spurting cum over the desk and his own legs. Donnie followed moments later, and Casey felt his climax fill him, cum trickling out of his rear as the turtle tentatively withdrew.

The reality of what they had done began to descend on them, and they adamantly avoided each-other's gaze as they cleaned themselves up. Casey was buckling his pants back up, one hand full of sticky tissues, when Donnie tapped him on the shoulder.

"Uhm, we're… we're not gonna tell anyone about this, right?" He asked hesitantly.

Casey shook his head firmly. "No. Nobody ever hears about this." After a pause, he added, "Except April, obviously."

"Well, at least she's going to get what she wants," the turtle remarked, a nervous smile on his lips. "It's not cheating if she asked us to, is it?"

This time, Casey actually laughed, finally relaxing. "Nah, it's not cheating. Besides, I'm pretty sure once she hears about this, it'll be happening a lot more often."

"And you're okay with that?"

"… Yeah." Casey shrugged. "Are you?"

Donnie's eyes drifted over the human's lean, toned body, focusing particularly on the trouser zip that hadn't been pulled all the way up. "Yeah."

Inspired by Andrea O'Down's 'About Her' and Lexifer666's 'Three's A Crowd' - both fantastic reads by fantastic authors and well worth checking out