Casey knew he was an idiot as soon as he entered the lair.

He’d been told not to, of course. Told by Raph, told by April, told by Splinter. Of course he didn’t listen. When did he ever listen? Besides, he needed that tape back from Raph, and he definitely couldn’t wait a whole month for that.

Seeing Raph fucking Leo made him wish he had.

And it’s not like he’s just seeing it now. No, he’s watching, and soon enough they’re watching him watching them and– oh, oh god. Did Raph just growl at him?

Casey gulps, starts to walk backwards as Raph makes that noise again. Doesn’t get very far. There’s junk scattered all over the floor and now he’s flat on the ground, nursing his back and his foot as he stares at the turtles in front of him. Raph’s still fucking Leo even with his attention diverted, but despite his blatant erection Leo’s not looking so happy.

No, Leo’s glowering at Casey. Glaring at him like he’s stolen something from him, and that’s when Raph decides he’s had enough of his older brother. He discards Leo to the side like he doesn’t even exist, and Casey can see it now. Raph’s thick cock is out in the open, leaking and throbbing and Casey’s too awestruck to look away until Raph begins sprinting right at him.

“Aw shit!” He’s too slow. Casey barely misses vaulting the turtle over his head him and now he’s on top of him and oh god. Raph’s beak is buried in the crook of Casey’s neck and he’s sniffing him. “–Fuck, dude! Get the hell offa me!” He doesn’t, and Casey can’t move him because Raph’s got him pinned. Raph growls again and Casey squirms, helpless as Raph begins rubbing against him- no, fuck. Raph’s humping him!

Fuckfuckfuck! This is not good. “Shit, Raph! Snap outta it!” The turtle ignores him; just keeps bouncing his cock on Casey’s crotch and sniffing at his neck and oh this is all so, so fucked up but Casey can’t help but feel his dick harden under Raph’s and shit – shit!

Something slams Raph off of him and he’s grateful – so grateful that Splinter or April found him until he hears the growling and realises that it wasn’t either of them that saved him. Leo’s beating the crap outta Raph, and Casey can only hope that Leo’s come to his senses or something as he hightails it out of the room, hope fading fast as the sounds of sex quickly replace those of violence.

The dojo’s quiet at the least, he thinks. It’s totally empty, like it hasn’t been used at all for a couple of days, but there aren’t any turtles that want to fuck his brains out. Master Splinter’s nowhere in sight either. Casey checks the side room, too. He’s gone. Do rats go on vacation? He can’t even smile at his own joke after Raph tried to screw him. The thought alone makes him shiver and he doesn’t even notice Donnie until he’s right behind him.

“Shit!” Casey panics, swings his arm round wildly, gasps as the turtle simply deflects it. He waits, waits for Donnie to make a move, to start growling at him like Raph and Leo – but he doesn’t. He just stands there, and Casey can only take that as a good sign. Or better than the alternative anyway.

He moves to speak again, but Donnie doesn’t give him the chance. The turtle grabs his arm roughly and he’s being dragged out of the dojo and into the lab. Donnie doesn’t even blink as he passes Leo and Raph, like seeing his brothers fuck each other like animals is the most normal thing he’s ever seen in his life. That worries Casey, but by the time he considers running Donnie’s already slammed the lab door shut.

The room’s so messy that he has trouble moving, but he manages to stumble his way across from the door. “What,” Deep breathing. Casey collapses against the wall, eyeing Donnie as he moves over to his desk and picks up some kind of syringe, “–the fuck, is going on in here?”

Donnie doesn’t answer straight away, which again strikes alarm bells in Casey’s head. He sweeps the room for some kind of escape route. Nada. Then Donnie turns to face him, and his expression is so completely calm that it puts him even more on edge. It’s too forced, like he’s straining to pull it off.

“Mating season.” Donnie says simply, taking a step towards Casey, and that alone almost makes him completely lose it. He tries to move, tries to kick all the scientific junk away from the floor so he can get away, but Donnie’s already right in his face. He’s trapped, and for the first time Casey starts noticing the little details; the erratic breathing, dilated pupils, the excessive sniffing– the bulge in Donnie’s lower plastron.

“No.” He tries to sidestep the turtle, but Donnie’s arm shoots to the side of him to block him. Then shell meets cloth and Casey finds himself crushed against the wall, Donnie’s other hand gripping him fast as he begins struggling. Shit! This cannot be happening! Donnie leans in and presses his nose to Casey’s own, and the smell hits him like a truck. Then he feels the prick of the syringe in his neck and his head fuzzes. It’s so startling that Casey barely reacts when Donnie pulls him into a kiss, and even throughout the fucked up moment he can’t help but breathe in Donnie’s scent because it’s just so good.

Donnie’s cock is out now, and Casey can feel it against the growing bulge in his jeans. It’s shameful. He shouldn’t be turned on by this, shouldn’t be enjoying it but Donnie just smells so enticing and inviting that he can’t help but give in. His head’s swimming and everything just seems so right, like he’s supposed to just give in. Give in. Give in to Donnie. Can’t help but give in as Donnie forces him to the ground, give in as Donnie tears his pants off, give in as Donnie lines up his dick with Casey’s hole and pushes in.

Casey can’t help but give in.