One morning in New York city, the Rainbooms were in Applejack's truck, as A.J drove through the city. They looked around seeing the city was enjoying a time of peace now that Shredder and the Foot Clan were gone, no Kraang to cause trouble, or even new mutants. Sure there were the Purple Dragons, but even they knew better than to cause any real trouble in broad daylight.
“Ah, New York, New York.” Rarity said happily.
“It's a heck of a town!” Pinkie cheered.
“And for once it's normal.” Sunset Shimmer put in.
“Hang on, Ya'll. We're comin' up to the entrance.” Applejack warned them, as she made a turn down an alley.
She pushed a parking garage button and the secret entrance to the sewers revealed itself, as she drove down it.
Once in the abandoned subway system, A.J parked her truck and they scrambled out, “I wonder what the guys wanna show us that's so important?” Twilight wondered.
“Knowing Donnie he's got something new cookin'.” Rainbow replied.
“Doesn't he always?” Fluttershy asked.
“Come on, let's go see." Pinkie said, as they followed the tunnel to the turtles lair.
They looked around seeing no sign of their ninja friends, “No one's here.” Spike looked around.
“Hello!” Twilight called, “Leo? Guys?”
“In the lab, girls!” Came Leo's voice.
So the group went to Donnie's lab and opened the doors. Upon entering the saw their turtle friends along with the Mighty Mutanimals.
“Hi, girls.” Leo greeted.
“Good to see you all.” Twilight said, as she hugged Leo.
“Mikey! Leatherhead! I missed you guys.” Pinkie hugged her favorite mutants.
“Same here girl.” Mikey agreed.
“It has been some time.” Leatherhead agreed.
“Hey, there, Fluttershy.” Slash greeted.
“I'm so glad to see you, Slash.” Fluttershy smiled.
“Hey, Doc, you using new polish on that helmet of yours?” Rainbow inspected Rockwell's helmet.
“If you must know, yes.” Rockwell confirmed.
“Hey, what's up, Spike, my dog?” Bandit Raccoon asked, as he and Spike slapped some paw.
“Nice to see ya, Bandit.” he replied.
Mona Lisa looked around, “Where is the Professor?”
“Fugitoid's back at home feeling he needed some time to himself.” Sunset answered.
“What could Fugitoid be doing all by himself?” Mikey asked, unaware back at Sunset Shimmer's place the android was dancing to some of the Rainbooms music on a CD while waving his hands in the air.
"Shake your tail 'cause we're here to have a party tonight!" Fugitoid sang.
“Anyway, what's this big surprise you have to show us?” Twilight asked.
“Well, after our countless dimension trips I’ve been reworking on my portal projector to check out other worlds.” Donnie explained.
“I chipped in a lot with the upgrades.” Rockwell boasted, much to Donnie's irritation.
“And we wanna test it out and wondered if you girls would be interested.” Donnie finished.
“Well, after going to such different places like Gotham and all, I'd like to see where else you have in mind.” Rainbow admitted.
Pigeon Pete got a look at the girls, “Hey, you girls are wearing your geodes differently.”
Indeed the mutant pigeon was right. The girls were indeed wearing their magical geodes differently than just necklaces. Twilight, Fluttershy, Pinkie, and Applejack wore theirs as headbands, Rainbow was wearing hers as a wristband, Sunset's was on her belt, and Rarity's was stitched to her shirt.
“Why yes we are, Pete,” Rarity confirmed, “We've decided to accessorize with them.”
“And so that they're not all hanging by our necks.” Applejack added.
“I think it's good for you girls.” Leo admitted.
“Thanks, Leo.” Twilight replied, as Leo smiled.
“So we going to do some more dimension exploring, or what?” Pinkie asked excitedly.
“Shouldn't we wait for I don't know, April or Casey?” Sunset Shimmer asked.
“April and her dad are back at their family farm house trying to remodel and refurbish it.” Donnie explained.
“And Casey's practicing for a hockey match coming up.” Raph added.
“What about Karai and Shini?” Fluttershy inquired.
“They're busy training some new Foot Recruits.” Leo answered.
"And Keno?" Rainbow asked.
"Working extra shifts at Antonio's." Mikey answered.
“So it's just all of us?” Spike asked.
“Pretty much.” Mondo replied.
“Well, at least we got each other.” Fluttershy said.
Donnie started setting coordinates for his portal device and projected a portal, “Alright, here we go.” Donnie said, as they entered the portal together.
The mutants, girls, Mona, and Spike screamed as they flew through the dimensional limbo before reaching the other side.
A portal opened above ground and they all fell through and landed in some alley, “Oh, wipe-out!” Mondo groaned.
“Why can't we ever land softly?” Mikey asked, as they got up.
“That's something I'd love to happen.” Came Rarity's voice.
When the mutants looked over and saw the girls their eyes widened, “Uh, girls.” Leo began.
“What?” Fluttershy asked.
“What's wrong?” Sunset Shimmer asked.
“You guys got an extreme makeover.” Bandit warned them.
“What do you mean?” Rarity asked, before pulling out her compact mirror and looked at her reflection seeing she had the face of a pony and had a horn on her forehead. She gasped before letting out a high pitched scream.
And it didn't stop there, the Rainbooms looked at each other seeing they also had pony faces and tails as well, while Twilight and Sunset had unicorn horns like Rarity, and Rainbow and Fluttershy had wings.
“We're ponies again!” Twilight cried.
“Actually, you look like Blade Swipe.” Mikey noted.
The girls looked at themselves and saw despite their pony features, they still had the physiques of humans, including hands.
“You're right. We're like pony mutants.” Sunset gasped.
“Awesome!” Rainbow cheered.
“No! I don't wanna be a mutant!” Rarity cried, as the other mutants scowled, “I mean, for you all it's good.” she said sheepishly.
“Hey, Twilight. I feel weird here.” Came Spike's voice, as they saw Spike walk over. Surprisingly, he was walking on two legs, and his paws had fingers.
“Spike, you're walking on two legs.” Twilight gasped.
“Yeah. Sure feels different.” Spike admitted.
“D, what's going on?” Rainbow asked.
“Well, let me see...” Donnie tried to find an answer, until Fluttershy gasped.
“Oh, my. I think you should all see this.”
The group peeked out of the alley and were shocked. They saw they were in some western town, and what was more surprising, the residents there were all anthropomorphic animals. Mostly cattle.
“Great Scott.” Rockwell gasped.
“Where the shell are we?” Raph asked in shock.
“We must've landed in some kind of alternate reality like Usagi's,” Donnie theorized, “Only this time the dimension we've landed in is some old western setting.”
“I sort of feel at home.” Applejack admitted.
“So what do we do now?” Spike asked.
“Let's go mingle with the people.” Mikey suggested, as he was about to step out, only for Raph and Leo to pull him back.
“Mikey, are you crazy?!” Raph scolded him.
“What? They're walking animals, we're walking animals.” Mikey noted.
“Technically you're reptiles.” Rockwell corrected him.
“Point is, we're like them so we got nothing to hide.” Mikey made his point.
“Still, we're in a western town. And we don't look like we're from around here.” Twilight motioned to her outfit.
“Yeah, and if we went out there like this we'd be considered naked.” Slash said, motioning to Spike and the mutants who weren't wearing any type of clothing.
“We're gonna need to blend in.” Sunset Shimmer suggested.
“And I know just the thing.” Rarity smirked, as she already got to work.
Soon enough, the Rainbooms, the turtles, Spike, and the Mutanimals all stepped out wearing cowboy/cowgirl attire, “Great job, Rarity.” Leo admitted.
“Thank you, darling.”
“Now we really look like we fit in.” Bandit checked himself out.
“I feel ridiculous.” Mona said as she looked her attire over in concern.
“Oh, nonsense, Mona,” Rarity said, “You look divine.”
“I'll say.” Raph agreed.
Mona blushed, “Well, if you think I look good, Raphael. Then I am ok with it.”
“Come on, let's check this town out.” Rainbow said, as the group started walking around trying to keep it cool, but still received looks from several citizens.
“Unbelievable. We get all dressed up and we're still getting looks.” Raph grumbled.
“Maybe because they know we're not from around here.” Twilight whispered.
“Where is here anywhere?” Slash asked.
“Look there.” Leatherhead motioned to a sign.
“Cowtown.” Sunset Shimmer read.
“Sounds too on the nose.” Raph remarked.
“I think it's clever.” Pinkie admitted.
“So what's next?” Bandit asked.
“Well, since we know what this town is called it's best to try and understand its history.” Rockwell explained.
“And there's no better place to learn history then...” Twilight began.
“Don't say it.” Rainbow cringed.
“A library.”
“Doh!” Rainbow groaned.
“Well, Twilight has the right idea.” Leo admitted.
“And it's right over there.” Donnie motioned to the town library.
“Then let's go.” Slash said, as they pressed on.
Later on inside the library, the group was sitting at a table looking bored, until Twilight and Rockwell came over with a big book, “We found the history book we needed.” Rockwell began.
“Though I wish everything here was better organized.” Twilight sighed.
“So did you find anything about this world's history?” Applejack asked.
“Oh, we found plenty,” Twilight confirmed, as she opened the book to a specific section, “According to this, a long time ago a comet came down from the heavens and struck this land raising a mesa to the sky above the clouds.”
Rockwell continued, “And everything atop the mesa had underwent a type of mutation resulting in the anthropomorphic animals we saw outside.”
“So that comet was some kinda mutagen comet?” Mikey asked.
“In a sense yes,” Twilight admitted, “Over time the animal folk that mutated started adapting into society creating their own community here. And the mesa was from then on called Moo Mesa.”
“Moo Mesa?” They asked.
“That sounds even more on the nose.” Raph said.
“Well, at least we're not dealing with evil magical wolves.” Leo replied, while recalling the evil Wolf named Jei.
“So what do we do now?” Mona asked.
“I'd like to look around some more,” Rarity suggested, "See how these western folk like to accessorize."
“Yeah. Let's see how these folks live it up here compared to home.” Applejack agreed.
Suddenly they heard a commotion outside, and they went out to scope it out. They saw causing a ruckus was a bunch of frog men dressed as outlaws. They were running around shooting stuff only instead of bullets coming out of their pistols it was all card symbols like spades, clubs, diamonds and hearts.
“Looks like we got us a throw down here.” Applejack gasped.
“Should we do something?” Mondo asked.
“I don't know if it's our place to get involved.” Leo said unsure.
“Come on, Leo,” Raph playfully slapped his shoulder, “We're here. There's danger. Let's do something about it.”
“Ninja Cowboy style.” Mikey added.
Leo sighed knowing there was no arguing with them, “Alright. But we have to be careful.”
“No problem.” Pinkie said, as the group armed themselves.
The outlaws were carrying some safes filled with money, and were loading them up in a wagon, “Let's get getting' on out of here fast.” one of the outlaws told the others.
One of the outlaws in the wagon grabbed the reins of the horses, but were suddenly cut by a kunai. The horses took off, leaving the outlaws stranded with their wagon. They looked ahead seeing the heroes, “Leavin' so soon, partners?” Sunset asked with a western accent.
“It's rude to just pick up and leave, you know?” Rarity asked.
“Who in tarnation are ya'll?” one of the outlaws asked.
“We're the guys about to send ya to the big house.” Slash warned them.
“That's right du-I mean, partners.” Mondo added.
“Take 'em!” the lead outlaw called, as the rest of them started opening fire on the heroes who spread out.
Leo jumped in and used his swords to slice some of their guns in half, while Twilight used her magic to levitate others out of the outlaws hands.
“Yee-haw!” Applejack called, as she dodged some of the ammo and delivered a powerful kick to one outlaw making him land right into a barrel.
Bandit jumped from a roof and landed on one of the outlaws heads and blinded him by pulling his hat down so low it covered his face, “Who turned out the lights?!” the outlaw stumbled around as Bandit clung to his head snickering.
Donnie used his bo-staff to trip some of the frog men off their feet, as Mikey swung his chucks around nailing some in the head. Raph and Mona were tag teaming against two more outlaws using hand to hand combat, “This is certainly unlike any kind of fight I've ever been in.” Mona admitted.
“Well, it still makes for a good experience.” Raph admitted.
As more outlaws tried to grab more safes, Leatherhead dropped in and roared at them. The outlaws dropped the safes and ran for their lives. Pinkie grabbed some sprinkles, “Here's a little something from me.” she threw the sprinkles at some outlaws that exploded. The crooks were blinded by the explosions, allowing Rainbow and Mondo to zip over and wrap some of them up with a lasso.
“Oh, yeah!” Rainbow and Mondo high fived.
As Rarity was using her diamonds for shields she saw one outlaw was about the shoot her friends, “Rainbow! Mondo! Look out!”
The two looked and saw the outlaw about to shoot them, only for his pistol to get shot out of his hand. The group looked over and saw three more figures enter the fray. All three were actual Cow Boys. One of them who was wearing a badge on his chest looked like an orange furred cattle, the second was a strong blue bull, and the third was a skinny black and white colored cattle.
The cow with the badge blew some smoke away from his pistol and spoke, “Looks like the party started without us.”
“Eeyup.” the blue bull answered, making A.J blink as if she saw her older brother.
“Well, that's a bust.” the third cow groaned.
“It's Marshal Moo Montana!” an outlaw cried.
“Right you are,” the supposed marshal confirmed, before turning to the heroes, “Mind if we join in at the last minute, fellas?”
“Uh, not at all.” Leo answered.
To the heroes surprise, the three cowboys made quick work out of the rest of the outlaws with the marksmanship, lassoing, and strength.
“Whoa.” Slash gasped.
“That blue dude's probably as strong as Rocksteady.” Mondo said in awe.
“These dudes are awesome!” Mikey cheered.
“No kidding!” Rainbow cheered along.
Suddenly the bandits were all rounded up and hogtied, along with all the safes filled with money they stole returned to the bank. The citizens cheered and applauded for the whole group, as Leo spoke up to the marshal, “Hey, thanks for the help back there.”
“Not a problem, friend. Welcome to Cowtown.”
The Turtles, Mutanimals, and Rainbooms knew this was going to be quite the experience they would never forget.