Hello to one and all. I would like to clear something up real quick; this crossover between Avatar: Last Airbender and Ninja Turtles features the Turtles from the previous, 2003 series (NOT the current 2012 series). This was a fic I've wanted to do for a while, and expect some minor AU alterations to the TMNT story line a bit later on; don't worry, I'm keeping all the characters the same. Oh, this is in the same timeframe of Season 3 for TMNT and Book 2 of Avatar. So then, now that's settled, let's get started.

Disclaimer, I own neither Avatar, nor Ninja Turtles, both franchises are owned by Nickelodeon.

Worlds Collide

Deep underground, far below the streets of New York was a massive shrine mounted on a large pyramid-like structure. At the bottom of the pyramid we're Leonardo, Donatello, Michelangelo, and Raphael, the Teenage Mutant Ninja Turtles. They we're at that moment surrounded by several dozen Foot soldiers, an organization run by their worst enemy, who currently stood at the top of the pyramid near a shrine of tall runes, that surrounded the center like a circle not unlike Stonehenge. At the top stood Oroku Saki, the Shredder; alongside him stood his right hand man, Hun; his adoptive daughter, Karai; and the rogue scientist, Baxter Stockman, now in his robotic form with a holographic head, as a shadow of his former self.

This wasn't any ordinary shrine however. This was the shrine for the Nexus, a gateway to the other worlds of the Multiverse, no doubt Shredder seeks to harness this power for himself, in his efforts to conquer the universe and destroy his enemies.

"Foot Ninja, Attack! Destroy them!" Shredder commanded from the top of the pyramid. The many ninja then charged forward towards the Turtles. "Karai, Hun, deal with those insolent reptiles! I need time to study the Nexus."

"Yes master." Hun and Karai both said at the same time as they bowed and went down to join the fight.

"Stockman!" Shredder commanded, startling the scientist. "How soon can you have this ready?"

"Deciphering ancient hieroglyphics takes time." Stockman answered as he looked at the runes decorating the shrine. Shredder glared, as he didn't like the answer "But I promise, I will have something for you soon."

Down below the Turtles we're busy sweeping past the many Foot ninja. Leonardo blocked the many sword strikes with his twin katana blades. Six Foot charged forward and brought their blades down, which Leo was fortunately able to block. He let himself fall down, bringing the six ninja down with him. He thrusted his feet forward, kicking the front-most two away. He jumped high and performed a splits-kick to the heads of two more ninja before slashing at the last two, knocking them back.

Donatello twirled his staff, reading for the incoming ninja. Five charged forward, but he was able pole-vault over them. He swiped his staff, sweeping two ninja off his feet. He blocked one sword from one ninja before kicking him in the gut. He twirled his staff again and bashed one ninja in the head with one end of his staff and smacking the last one across the face with the other end.

Raphael had an eager smile as five ninja slowly approached them. "Bring it on." He challenged before they all jumped forward and he rushed towards them as well. He ducked under one sword and gave a punch to the gut of one ninja that sent him flying. He blocked another slash from the sword with his sais and snapped the blade off with a twist before kicking him hard in the face. A third tried to attack from behind but Raph grabbed him and threw him over to the remaining two, causing them to smack into the wall of the pyramid.

Michelangelo found himself surrounded by six more ninja. He gave a smile as he spun like a top, twirling his nunchucks, bashing all six ninja and causing them all to fall to the ground as he still twirled his weapons and held his tongue out slightly. "Cowabunga."

"Guys come on!" Leo rallied. "We got to stop Shredder, now!"

"Don't have to tell me twice!" Raph agreed as they all began to run up the steps. They heard a loud yell however, and looked up to see Hun diving towards them. He grabbed Raph and Don before they smacked down into the ground. Leo and Mikey then heard a pair of swords being unsheathed and looked up towards the steps to see Karai wielding her own katana blades.

"Mikey, go help Don and Raph with Hun, I'll handle Karai." Leo told his youngest brother.

"Uh dude, you don't exactly have a winning streak with her." Mikey reminded.

"I can handle it, go!" Leo ordered. Mikey nodded before running down, leaving Leo to face Karai alone.

Raph and Don groaned as they got up to see Hun glaring at them. "Well, well." Raph greeted. "If it isn't my favorite Neanderthal."

"Uh, Raph, let's not try to antagonize the super villain." Don advised.

"Aw come on Don." Mikey complained as he joined his brothers. "Antagonizing them is always the best part."

Hun cracked his enormous knuckles. "I've been looking forward to this, freaks."

"You're one to talk!" Mikey commented. "Seriously, how does a guy even get muscles that big?! You hopped up on steroids or something?"

"That's it!" Hun yelled before charging forward, and the three turtles ran forward as well.

Hun jumped high and cupped his fists before brining them down onto the ground, forcing the three turtles to scatter. Mikey was first to go forward, flashing his nunchucks straight to Hun's chest, knocking him back a bit. It did little to deter Hun as he was more built than the average man. He smacked Mikey back before Don came in from behind and slammed his staff to the back of his calves, forcing Hun down on his knees before Raph came charging in sais first. Hun was however, quick enough, to grab Raph and throw him back to Don.

They groaned as they got up to see Hun slowly approach them with deadly intent.

Back on the stairway, Leo continued his sword duel with Karai, though Leo was holding back a bit.

"Karai, how are you still serving him?!" Leo questioned as he locked blades with her.

"You already know the answer to that, Leonardo." Karai responded as she threw her swords forward, forcing Leo to step down the stairway, as he was now on the defensive end.

"Do you even know what this place is Karai?" Leo asked as he ducked to avoid a slice from her left blade and blocking her right blade with both of his.

"Yes, this is doorway to the Nexus." Karai began. "A pathway to countless other worlds."

"And did you ever stop to ask yourself, why Shredder is looking into this place?" Leo asked again as he continued to block Karai's strikes. "It's because he's looking for another world to conquer and abuse! Wake up Karai, Shredder's pure evil!"

Karai tried to sweep Leo with her feet but he jumped over her to the higher stairs before he took the offensive. "I'm sorry Karai." Leo began. "But if you still stand with someone like him, then I will stop you."

Leo now begun to attack, forcing Karai to take the defensive. His continuous sword strikes being blocked as he was forcing her down the stairway of the pyramid.

Back down below; Raph, Don, and Mikey we're defiantly giving Hun some trouble. They mostly stuck with hit-and-run attacks as they knew going one-on-one with a behemoth like him wasn't going to end well. Raph was first with a hard punch and a kick to the abs, knocking Hun back. He quickly got up and charged towards Raph who jumped back just as Donnie had now slammed his bo-staff at the back of Hun's head. He turned around to try and smash Don, only for him to jump back as well. Mikey was next with multiple nunchuck-smacks across the face, causing him to yell in pain and hold his bruised face.

Raph, Mikey, and Don all nodded to each other, as it was time to press the advantage. Hun opened his eyes just in time to hear their conjoined yell and see all three of them leaping high into the air and delivering fierce kicks; knocking Hun back to the wall of the pyramid and finally knocking him out.

"Sleep tight, Hunny. Don't let the bed-bugs bite." Mikey cracked as he, Don, and Raph all high-fived.

They looked up to see Leo finishing his duel up with Karai. She continued to block his assault. Leo slashed to the left, which she blocked, but he gave a kick to her chest forcing her back. He then swipped both his blades, knocking both of hers out of her hands. Leo finished by grabbing her arms and pinning them behind her back. He put his finger to a pressure point in her neck area, forcing her to loose consciousness. He gently set her down to the side. Karai may be the enemy, but she's not like the Shredder, and he wasn't about to harm her like he's planning to do for him.

"Geeze, don't be so hard on her or nothin'." Raph said sarcastically as he Don, and Mikey caught up.

"That all of them?" Leo asked, ignoring Raph's comment.

"Yep, that's all of them. Hun and the last of the Foot are taking a little nap." Don answered.

"Good, then it's time we pay a visit to an old friend." Leo stated.

"Stockman. I grow impatient!" Shredder said.

"I'm working as fast as I can!" Stockman exclaimed as he continued to despiser the ruins.

"Well work faster! Unless you'd like to receive further punishment." Shredder warned darkly, forcing the frightened, evil, scientist to work faster.


The evil leader of the Foot turned to see Leo, Raph, Don, and Mikey all arrive, battle-ready, and glaring at their nemesis.

"Ugh! Failures! All of them!" Shredder exclaimed, referring to his subordinates. "I grow tired of you mutant freaks and your constant interference."

"Get used to it bucket-head!" Raph exclaimed.

"If it's what you prefer, I will finish you myself!" Shredder declared as he brandished his claws. "Stockman, continue your research, I will deal with these annoyances."

"Yes master." Stockman replied, not willing to argue with him.

The Turtles we're the first to charge forward. They all rushed him at once hopping to get the advantage. They we're proven wrong as he swiped them all back with a massive sweep of his legs. He ran forward this time, and they quickly dispersed.

Mikey and Raph charged in from behind, only for him to smack them back towards the center. Leo and Don stood in front of their downed brothers as Shredder ran forward again. Leo blocked a slash from Shredder's claws with his swords before Don tried to smack him in the side with his staff, only for Shredder to quickly kick him away. He grabbed Leo by the throat and threw him towards Don. Both rolled into the ring of stones that surrounded the center.

However, it seems the failed to notice the ruins and hieroglyphics on the stones began to glow a faint cyan blue color. It seemed the only one to notice this was Stockman as he began to look at them with interest.

Mikey tried to attack Shredder by flailing his nunchucks towards him, but Shredder was too quick for him to make contact. Shredder then thrusted multiple palm and fist strikes forward, the last one smacking into Mikey's face, knocking him to the very center of the circle of ruins, causing them to glow slightly brighter.

Raph was next as he lunged his sais forward. He was able to successfully scratch Shredder's armor a bit. But it only served to anger him as Shredder slashed towards Raph with his claws, forcing Raph back a bit. Shredder gave a hard kick to Raph, sending him flying onto the barley conscious Mikey at the center of the circle, causing the ruins to glow even brighter.

Don tried to strike Shredder across the head, but he quickly caught the staff in his hand before kicking Don back, who quickly flipped to his feet but it wasn't quick enough as Shredder was now standing in front of him. Shredder gave a hard right hook to send Don rolling across the ground towards the injured Mikey and Raph, which seemed to cause the ruins to glow even brighter than before. Stockman was now getting slightly worried at this point.

Leo stood there, swords at the ready. The two foes glared at each other before charging forward with yells. It was a great storm of metal clashing with metal. Leo was fast enough to keep up with Shredder, but not fast enough to attack, just defend himself. Shredder slashed with his claws repeatedly as Leo continued to block each strike that was dealt to him. Leo was able to kick him in the chest to force him back. The blue-clad Turtle then tried to press the advantage and charge forward, but Shredder caught both his blades in his claws before throwing them away, and landing near his downed brothers. Shredder then plunged his claws into Leo's abs earning a gasp from him before Shredder picked him up and threw him towards his brothers.

Shredder's claws dripped with blood as he slowly walked towards them. "At last, the end has come to you turltes."

However, the ruins quickly began to glow to a bright white. Stockman was forced to cover his eyes.

"What?!" Shredder questioned as he saw the ruins glow and the downed bodies of his enemies began to glow as well as it looked like a bright blue sphere of energy was encasing them. "The Nexus?! It's activating?! No!" He ran towards them.

Suddenly there was a sudden flash of light that flashed throughout the entire underground chamber; forcing Shredder to shield his eyes. Hun, Karai, and all the downed Foot Ninja woke up to this light and looked in amazement at the top of the pyramid before the light vanished.

When it did, Shredder looked to the center of the circle, only to see that his enemies we're no longer there.

High in the skies of the Earth Kingdom, Appa the Sky Bison, and the fateful companion of the Avatar soared above the landscape. At the reins was none other than Avatar Aang; sitting behind him in the large saddle we're his friends Katara, Toph, and Sokka.

"How long have we been flying on this thing? Can we please set down? I hate not being able to see." Toph complained.

"It's a lot faster this way than just walking Toph." Sokka told her.

"Hey, I'm still new to your little group, remember? I'm not quite used to flying." Toph replied.

"Don't worry, you'll get used to it." Katara assured.

"So, guys. Anyone got an idea of where to go to next?" Aang asked.

However, before anyone can answer; they noticed a large flash of white light coming down from the forest far below. Aang was forced to stop his bison in the air, causing it to hover as they all shielded their eyes, minus Toph. The flash died down soon after.

"What the heck was that?!" Sokka exclaimed.

"What? What was what?" Toph questioned.

"A bright flash of light, that's what." Katara answered. "Any idea what that was Aang?"

"No idea." The Avatar answered. "But I'm gonna find out." He pulled on the reins and Appa began his descent towards the forest below.

Mikey, Raph, and Don groaned as they slowly got up.

"Ugh. Did anyone get the number of that psychopath who ran us down?" Mikey partly joked.

The Turtles looked at their surroundings and found themselves in the middle of a forest.

"What the… Where the shell are we?!" Raph exclaimed.

"I haven't the faintest idea." Don replied. They heard a certain groan, which caused them to look down towards to the ground, and their faces became filled with shock.

"Leo!" Raph exclaimed as he, Don, and Mikey kneeled to their lying brother. They looked to see the bleeding wound on his chest, which Don quickly covered with his hands.

"Don, is he gonna be okay?" Mikey asked with concern.

"His wound is pretty deep. He needs medical attention quickly." Don informed.

Raph growled in anger as he clenched his fists. "If I ever see old Shred-head again, I'm gonna…"

"Did you guys hear that? It sounded like voices?"

The three Turtles turned to the sound of that voice towards the sound of leaves rustling in the woods near them. The Turtles looked to see four kids walk out into the clearing only for three of them to stop with wide eyes as they saw the mutant turtles standing before them.

There was a brief moment of awkward silence between the two groups, which one of the kids seemed to pick up.

"Uh… guys? What are we looking at?" Toph asked.

"Oh nothing." Katara began, her eyes not shifting from where they still are. "Just four walking, talking, turtles."

Oddly enough Toph gave an amusing smile. "Cool."

"Well…. This is awkward." Mikey spoke out loud.

Sokka then quickly pulled out his boomerang and pointed it to the turtles. "Demons! We got demons!"

"Really? Demons?" Don questioned nonchalantly.

"First aliens, now demons? Geeze where do people come up with these excuses?" Raph questioned.

"Who or what are you guys?!" Sokka demanded.

"Whoa, Sokka hold on. We don't know anything about them." Katara tried.

"I don't care! You don't see giant turtles everyday!"

"Oh, just because we're out of the ordinary, you think we're evil or something?" Raph questioned. "This coming from a wimpy kid with a pony tail."

"Hey! This is a warrior's wolf tail! Very manly!" Sokka exclaimed with a high pitch voice.

"Just about as manly as that girly voice of yours." Raph cracked, earning a glare from Sokka.

"I like this guy already." Toph whispered to herself.

Before anyone else could say anything, Leo groaned again in pain as Don continued to try and support him and hold his wound. "Raph, we don't have time for this."

Aang noticed the blood coming from the wound of one of the Turtles. "One of them is hurt!"

"Yeah, no duh baldy." Raph replied harshly.

"Raph." Don lightly scolded. "Listen, we don't mean you kids any harm. Our brother's hurt and he needs immediate medical attention."

"Seriously, you guys know a doctor or something we can take him to?" Mikey asked.

Aang and Katara looked to each other with worry. "Maybe I can help." Katara said as she walked forward but Sokka held his arm out in front.

"No, it's a trick! It's gotta be."

"Sokka!" Katara scolded.

"What?! We just find four demon turtles, and one of them just happens to be hurt? I'm not buying it."

"He's freaking bleeding! What more do you want?!" Raph angrily stated. "Or maybe you'd like it if I make you bleed a little!"

"Is that a threat?!" Sokka questioned.

"It is if you're gonna try and hurt my brothers, kid!" Raph drew his sais.

Aang quickly stepped between the two before anything could start. "Sokka, no! We gotta help them."

"Why?! That one in red just threatened me!"

"You threatened him first." Toph corrected. "And for the record, they're telling the truth."

"How do you know?" Sokka asked.

"When people, lie there's a physical reaction, I can sense that. And their not lying." Toph explained.

"Sokka, let me help him. He's hurt, what kind of people would we be if we let someone die?" Katara told him.

Sokka sighed as he was forced to concede. "Fine."

Don and Mikey lowered the injured Leo gently on the ground and set his head onto a large rock to prop him up. Katara kneeled down and saw the wound and looked with surprise, it was very deep, and it looked a bit like it was done with some form of claws.

"Can you help him?" Don asked.

"I think so, yeah." Katara replied as she opened the cap on her satchel and began to pull some water out, much to the surprise of Raph, Don and Mikey. Katara then bent the water around her hands in the form of a blob and placed it over Leo's wound, which began to glow a little bit.

Leo clenched as the water set in, but he felt a strong sense of relief take over as the bleeding stopped and the wound began to close. He slowly opened his eyes and looked to Katara.

"Thank you."

She smiled and nodded in response; while his brothers sighed in relief. Leo tried to get up, but a hand was extended towards him, it was towards the smiling Aang. Leo took his hand and was back up on his feet.

"How you feeling bro?" Mikey asked.

"Much better." Leo replied.

"You had us worried there for a second." Don told him.

"Not me." Raph said. "You're as tough as they come, no way you're letting a little cut get you down." Leo gave an amused response to his brother's gesture.

Toph could tell Raph was bluffing but chose to keep quiet.

Aang then spoke up. "So… who are you guys exactly?"

"I was about to ask you the same thing." Leo replied.

Done. The Turtles have now met the Gaang. What adventures are in store for our heroes?

Find out on the next chapter of Worlds Collide.