This is based on my headcanon over at AO3. Raph is an alpha turtle, Leo and Don are neutral, and Mikey is a purely submissive turtle. In this, the turtles had to flee their home and traveled dimensions for a while, until they found a dimension full of humanoid turtles, just like them. For more Information look up my AO3 works, username is Queen_B.

Warnings: Contains Mpreg and necessarily minor OCs. Don't like, don't read.

Ever since they decided to stay in this dimension, the turtles noticed more and more similarities to earth.

They had cities, just like on earth. Shops, museums, night clubs, schools, everything. Okay, the shops were a little different, selling stuff turtles would need. There were no clothing shops because, well, no one wore clothes.

Food was different too. They were usual vegetables and fruits, or at least some similar ones. The candy was completely different and both Raph and Mikey had tried some nasty ones as they claimed. Some sauces and whatnot were good, some not. Fortunately they found enough earth-food.

They had a city hall too. And the turtles there were really friendly. When the Hamatos asked if they could stay, they were offered financial help. Since there were no martial arts schools yet, or anyone knowing about martial arts, it was clear that was something they could do.

There were so many children! Back then when Leo and Raph saved those turtle women some kids saw it too and the news spread amongst them like a fire. As soon as the dojo opened the doors were practically ran down by at least a hundred children. It was needless to say things were going good.

The Hamatos lived above the dojo in a four-bedroom apartment. Donatello had his own lab, and Raph his own weight room. Their living room had a huge tv and gaming console, and Mikey highly enjoyed his mornings by playing all those foreign games.

Anyways, coming spring they realized a big difference to earth.

"What... what is going on here? Donnie?" Leo didn't look at his genius brother. He was too busy watching at least three couples making out right in the middle of the street. They were already pretty far, and would be fucking soon.

"I have no idea? I've been here as long as you, Leo." The olive turtle jerked away as a group of three just started making out right next to them. All over the street, against trees, on parkbenches, slowly more and more couples and groups started making out. Some who were alone suddenly just joined a few others.

"This is really weird..." Leo gulped. "We should head inside..."

"Agreed. Mikey, Raph?"

When there was no answer, Leo and Donnie looked around for their mates.

"Oh my..."

Raph had Mikey pressed against the outer wall of their dojo, shoving his tongue down his throat. Mike churred softly and whimpered, pressing himself close to Raph's muscular body.

Leo and Donnie looked at each other in confusion and slight arousal before walking closer.

"Um... guys. Let's continue this inside." Leo put a hand to Raph's shoulder, who growled, ignoring him as he ravished Mikey's mouth. "Raph!" the leader spoke up louder in a stern tone.

Donnie watched with a frown. He just hoped it wasn't like back at home when they almost raped each other. He grabbed a bottle of water from his bag and opened it quickly, pouring the contents over their hothead brother.

The effect was instant. Raph gasped and jerked back, wiping the water from his eyes.

"What the hell?!"

"Let's just go inside..." Leo glared at a couple that came dangerously close to them. The scent of sex filled his nostrils and with a blush on his face he pushed his mates inside, locking the door behind him.

"Mikey, what are you doing?" Don's voice was strained, and when Leo turned his eyes grew wide. His youngest mate's tail was flipped up, exposing his swollen entrance. The clear lubrication was already leaking down his thighs and wet Don's lower plastron as Mikey rubbed himself on him.

"I... I don't know..." Mikey panted, his face flushed darkly. "I want... I need... oh god..." He let out a loud whine, which was cut off abruptly when Raph grabbed him and pushed him on all fours. Automatically Mikey lifted his rump higher, perfect position for Raph to push his length into him. "Ah... yessss..."

Leo and Donnie watched with wide eyes. Their sex life was pretty good, but never did they start out so... uncontrolled. Usually it took a good amount of time before one of them became so needy.

Donatello had a feeling they should keep a clear head in all this, but his youngest mate's rubbing had him pretty aroused already. And looking down he saw Leo in the same state. Without anything better to do they started making out too, though a lot slower than their brothers.

Raph was picking up the pace, rutting into the tight hot channel. Mikey could only moan and churr, moving his hips to meet the thrusts. Raph reached his peak pretty quickly and released Mikey's hips when he pulled out.

"Fuck..." he panted and sat back to catch his breath.

"No... I need more..." Mikey whined, hips twitching as he buried his face in his arms. There was this urge. He needed to be mounted again. He needed it. He felt so empty.

"Gimme a minute, will ya?"

"P-Please..." Michelangelo was almost sobbing now. The empty feeling was unbearable. And then suddenly he was filled again. The cock was a little slimmer than Raph's but longer. Donnie. "Ngh yes..."

Leo watched with hooded eyes how the genius pushed inside their baby brother. He scooped up some of the dripping lube from Mikey's thighs and hurried to push a finger into Don. While the olive turtle fucked Mikey, Raph added a finger to Leo's, pulling him into a bruising kiss.

Something was very different. Both Raph and Mikey acted so desperate, not clear at all in their minds. Yet he couldn't find himself to care. Not when his younger brothers moaned so deliciously, and when Raphael's other hand fondled his tail so roughly.

"A-Ah..." Donnie came with a stuttered moan, thighs quivering with the force of it. As soon as he pulled out of Mikey, Raph took him aside and buried himself into the prepared hole.

"L-Leo, please!" No, the leader couldn't ignore such a plea from his baby brother. So without further ado he positioned himself and quickly inserted his cock into the winking entrance. Leo hissed at the feeling. It was like Mikey was burning from the inside, and it felt incredible around his dick. He reached around to grip Mikey's cock, jerking him off quickly, but the youngest squirmed and pushed his hand away.

"No... it's too much... just... fuck me... please..."

Only a few thrusts later Leo emptied himself too. He pulled out and watched his semen – mixed with Raph's and Don's – oozed out of the still twitching hole.

"M-More..."

Raph used his grip on Donnie's hips to relocate him so the genius could penetrate Mikey again. With the double stimulation Don came pretty soon for the second time in half an hour. Raph relentlessly continued to fuck Donnie, who found himself squirming. He needed a little time to recover!

Mikey wasn't satisfied with the deflated cock in him. He needed more! He was beyond exhausted already, and he hadn't even come yet!

"Raphie..." he begged, rocking himself against the squirming Donatello. "Please..."

Raph growled and pulled out of Donnie, giving him two seconds to move away before he mounted Mikey again, eliciting churr after churr from both of them.

Leo and Don knelt next to each other, watching.

"I think this is some kind of heat... a mating cycle... It seems being here affects us just as much as the other turtles..."

"When did you have time to figure this out?" Leo shook his head at the genius, stroking his own hardened cock when they heard Raph reach his peak again.

"I need more..." Mikey whined breathlessly, squeezing around Raph's cock still in him. The hothead pulled out with a groan to make room for Leo again.

"How long... does it... last?" Raph panted, sitting on his butt and shaking his head.

"I have no idea..."

It took them about 36 hours. It was a chore getting up from time to time to get them something to drink to keep them hydrated. Mikey seemed to be insatable, unable to cum for a long time until he did and promptly passed out.

Too tired to move anymore, their cocks overly sensitive after fucking so much, they all just curled up on the floor of the dojo around each other.

When they woke up next they felt normal again. At least not horny anymore.

"Ouch..." Mikey rubbed his backside as he carefully stood up. It was too painful to sit right now. "Holy shell, what was that? I just got all hot and horny all of a sudden..."

"We went into heat..." Donnie sat up with a yawn.

"Oh great... Even I don't want sex for a while now..." Raph stated as he stood up too. "I mean, twas awesome and all... but I think my dick fell off." Mikey laughed and immediately winced at the pain shooting up from his back.

"I think you left it in my ass." he joked, leaning against his hothead brother with a sigh. "I really need a shower. Oh ew, your junk is leaking out." Mikey grimaced, pressing his buttcheeks together so it wouldn't run down his legs.

Raph chuckled and scooped him up bridal style.

"I think we all need a shower." And with that they headed off upstairs.