The four brothers stepped outside, and took in their surroundings. They raced down the street happily naked, their powerful legs beneath them. When they stopped, they felt their bodies bulking up more with muscle, their shells growing thicker. Zack and Axel started climbing up the walls of people's houses while Jack and Pablo swung on lampposts skillfully landing one their feet.
Eventually, they found a quiet lawn to sit.
"That was fucking awesome, man."
"Is every night going to be like this?"
"Shit man, stop poking me!"
"I'm not poking you-oh, that makes sense."
The turtles found that all four of their members were now stiff and hard, like green handlebars. Without thinking, Axel grabbed Jake's cock and stroked it. Jake nearly yelled at him to stop, but instead he did the same to Pablo. And Pablo did the same to Zack, who did the same to Axel.
It felt good to have three fingers going up and down on his cock, and when Zack felt the pressure building, he shot a decent load onto the grass, followed by Zack, Pablo, and Axel spraying their cum on the exact same spot as the circle jerk came to an end.
The brothers rested on the shells, unaware that a six-year old girl, Betsy, had seen them pleasuring themselves from her bedroom window across the street. Her parents had just gone to bed, so Betsy sneaked out through the backdoor and walked over. She poked Pablo's shell to wake him up.
Pablo's foot jerked back and kicked her. Betsy fell down face first, and when she tried to get up, her tongue accidentally tasted some of the dried cum on the grass. Betsy's skin turned green, her hair fell out, and a shell ripped through her pajamas. The brothers woke up to find a little turtle girl crying after seeing her now-mutated hands and feet.
"Zack, what the fuck is this? Now we've got a little sister?"
"We have to take her, at least until we can figure out how to fix this."
He carefully walked over to Betsy, who practically jumped into his arms and hugged his armored chest tightly. "Big brother, I want to go home."
"Umm, yeah, sure we can do that. Fuck, Axel, what the hell are we supposed to do with this?"
"I can call my neighbor. Maybe she'll know."