A/N:
Watch 2012 episode 'Deadly Venom', before reading this one-shot crossover, if you're concerned about spoilers.
Letting my imagination take form in this little one-shot crossover, I decided not to be consistent with some of the elements of TMNT canon-wise.
A full moon shown brightly in the sky that was filled with bright stars, casting its glow upon a thick dark forest. Time past by peacefully save for the hooting owls and crickets that dwelled there, until the peace was disturbed with two shadowy figures running at top speed towards a deserted traditional Japanese House, which was located in the middle of the forest.
One of the figures, the taller one, appeared to be carrying something over his shoulder.
The shorter figure opened up the slide door for his partner to the house. looking around, he made sure no one was following them, then slid the door shut from the inside.
The taller figure entered the first room he spotted, and placed the object he was carrying on a futon that was placed beside a window where the moon shown illuminating the figure that lay there; A blue masked ninja turtle wearing an initialized belt buckle.
Unconscious, with an arm wound. The only sign showing that he was still alive was his un even breathing.
"Shell!" The taller figure now sitting on the tatami floor on his knees gently grabbed his arm and examined it letting the light show his own blue masked face.
"I'm sorry. I should've sensed your fear of snakes. If I had known, I would've stopped you from joining us against Lord Hebi." He looked away.
"I guess putting on a brave act is a common trait between us, right?" the other figure stood beside his comrade letting the moon reveal him as a grey turtle "Hmph, no matter how scared we are we refuse to show it!" he smirked.
"I should've sensed it!" He felt the patient's head who's temperature got worse. "When I told him that we were going to face a giant snake, he gave a reaction that I couldn't make out at the time. I feel so foolish for not figuring it out too soon!"
"Hey, calm down, Bro." the grey Turtle put a hand on his shoulder.
"Calm down?!" He looked up at him with a frown "Can't you see, Prime?!" He stood up eyes fixed on his Prime self "The poison is slowly taking effect! He's going to die soon! And you are telling me to calm down!?"
Suddenly an angry Prime took out his katana and swiftly threw it towards the room entrance.
A quick yelp was heard followed by sound of the sword hitting a wall beside the room entrance.
"Show yourself!" Prime demanded as his taller counterpart took out his katana.
"Calm down guys! Its me!"
"Rookie?!" Prime narrowed his eyes as the one he called 'Rookie' emerged from the shadows letting the moon reveal him.
"Did you shake them off?!" Leo asked sternly.
"I almost didn't." he answered looking at Leo "They were about to catch me when a rabbit samurai appeared out of no where and rescued me. He fought them giving me a chance to escape without being followed."
"Usagi…" Leo quietly said
"Now where is he? Is he still alive?" He quickly asked concerned for their fallen comrade. When his blue eyes fell on him he pushed them both away taking a good look at him.
"Have you extracted the venom from his system?!" he frantically asked as he sat on his knees.
"No, we don't have the medicines to do so." Leo answered.
The younger Leonardo looked up at them "You mean you don't know the Healing Hand?!" he asked with a surprised expression as his eyes darted between them before he settled on Prime. He thought that his first incarnation from the the very first world that spawned the multiverse should've been a master in all form of Ninjutsu, including the Healing Hand, or at least a variant of it.
His attention then pulled back to the patient who's breathing pattern got worse and started to sweat uncontrollably.
The blue eyed turtle frowned then closed his eyes as he brought his hands together and started chanting a mantra.
Leo and Prime watched silently as their younger counterpart performed a number of jutsu hand signs with the foreign words that the two older turtles understood so well.
Leo watched with amazement while Prime raised an eye ridge as his body started to glow. He then picked up his pace as he performed the chant faster then suddenly placed his hands on the plastron of his comrade. All the glowing transferred to the sick body that glowed for a few seconds.
The two older turtles watched with amazement as the wound slowly but clearly healed and closed up.
Once the glow faded the blue eyed turtle removed his hand and sighed with relief, glad that his friend was out of danger and smiled as he watched him breath normally again.
A few moments passed before he heard a clapping hand. He looked beside him to find it came from the Prime Turtle.
"I have to admit; You're better than I thought you'd turn out to be, Rookie."
Little Leo blinked at him.
Since he met up with his counterparts, after the mysterious cross dimensional accident caused by Renet, and lead him to this ancient world, he never heard a good complement from this particular turtle. All he got from him were insulting words like 'Wanna-be' and 'sell-out'.
"Oh it was nothing." He blushed as he rubbed the back of his own head.
"Nothing?!" Leo intervened, placing a hand on his shoulder "You just showed a skill in a field that I have yet to master, and you're still sixteen!"
"Really? I'll take that as a complement then!" Blue-eyed Leo felt prideful.
"So any ideas when he's supposed to wake up?" Leo asked eyeing the now peacefully sleeping turtle.
"Oh he might take a couple of hours before he completely recovers. So we got plenty of time to plan our next strategy to get back to our own dimensions." He replied.
"Listen up, Kid!" Prime yelled as he shoved him with authority "I'm the one in charge here, so I decide what to do next, and you follow without question, got it?"
Regaining his balance after almost falling backwards, Little Leo was about to retaliate when he eyed the taller Leo who gave him a look that told him to calm down.
"Yeah, sorry about that." He rolled his eyes "So what do you propose we do next… Leader?"
Suddenly Prime grabbed the surprised turtle's arm and took him to the middle of the room and forced him to sit down on his knees.
"Get over here!" Prime ordered the taller turtle with a demanding hand gesture as he sat down facing the young one.
Leo mentally shook his head as we went to sit beside Prime. "If Mikey was here he would've giggled at a certain video game reference." He thought to himself.
Young Leo blinked at both of them as they silently watched him. Suddenly they said two words in unison.
"Teach us!"