The sun began to set on Ponyville as Twilight Sparkle's friends gathered with the Cutie Mark Crusaders in the castle. They would all spend the night together having a slumber party, fall asleep, and then ambush the Yo-kai that had been turning ponies into cats as soon as it arrived.

Even so, though, that didn't stop them from mixing business with pleasure as Pinkie Pie had collected snacks, while Rarity brought over a whole kit for makeovers. Rainbow facehoofed at the stuff Rarity bought, but she was still happy to be there to help Twilight catch the Yo-kai inspiriting the town.

"So, Twilight," Whisper began. "If you don't mind me asking, how exactly do you plan on catching a Yo-kai inspiriting your friends with a trap like this? Especially since it's a Boss Yo-kai..."

"I've been doing some modifications to the Yo-Kai Watch after what you said about the Boss Yo-kai. It took me five hours straight with no break, in addition to setting up this slumber party trap, but I think you might want to see this..." Twilight showed Whisper the Yo-Kai Watch and pressed down on the bubble dome.

The watch whirred to life as it extended out upwards, causing five extra Yo-kai Medal slots to appear on the side. The bubble dome then disappeared into the device as the clock face inside turned into a digital screen with six different boxes, most likely so that Twilight could keep track of her Yo-kai in battle. The last new feature was a small pen-shaped object extending out of the side of the transformed watch.

"Whoa..." Everyone looked in awe at Twilight's Yo-Kai Watch.

"Do you all like it?" Twilight asked as she showed off the fruits of her labour. "I call it: Yo-Kai Watch EX!"

"I've never seen the Yo-Kai Watch look like that in, well, EVER!" Whisper gently rubbed the side of the watch.

"By implementing a micro computer screen with a new release valve and extra Yo-kai Medal slots, this enhanced Yo-Kai Watch allows me to summon six Yo-kai at once, and then rotate them in and out of battle at a moment's notice." Twilight used her hoof to point out all of the important parts. "The screen, operated by this tiny little stylus allows me to have a front row and back row of fighters. The front row do all of the fighting, while the back row wait for their time to shine. It also allows me to prompt the Yo-kai to use their Soultimates whenever the need be, and if they get inspirited by the Boss Yo-kai, I've managed to put in a function to purify them." Twilight gushed over her masterpiece. "Science is so wonderful, isn't it?"

"You must be exhausted after working on upgrades like that, and set up this slumber party so we could help out..." Rarity looked at Twilight's eyes, seeing that her eyelids were starting to droop.

"Don't worry about a thing, Rarity." Twilight yawned and covered her mouth with her hoof. "By the time we beat this Boss Yo-kai, I can get a wonderful night's sleep and get ready for whatever monster comes my way, be it Yo-kai or otherwise."

"Does that Yo-Kai Watch allow you to see higher ranking Yo-kai too?" Whisper examined the screen, mainly looking at the six black boxes.

"At the moment, it's been calibrated to show just 'E' ranking Yo-kai in the world around us." Twilight rubbed the side of the watch. "I haven't exactly worked out all of the kinks yet, and 'E' rank is the only setting I can put this thing on without the Yo-Kai Watch exploding on my wrist."

"But it can detect Boss Yo-kai, right?" Whisper raised a brow at Twilight and the watch.

"Yes. Because Boss Yo-kai aren't in any real tribe, and have no official ranking on the 'E' to 'S' scale, the Yo-Kai Watch EX can uncover them with minimal effort." Twilight gave a smile to Whisper. "Not only did I remember everything you said, Whisper, but I also kinda looked at your little computer screen while you weren't looking..." Twilight blushed.

"I sure do hope that it won't stay that way forever, though." Pinkie Pie looked at the watch herself. "I kinda liked the old one better, if I'm being totally honest. It was so small and cute!"

"Don't worry, Pinkie." Twilight used her magic to revert the Yo-Kai Watch back to its' original form. "The Yo-Kai Watch EX is only for when we're entering hostile environments, or facing up against the Boss Yo-kai that Whisper warned me about."

"Uh, Twilight?" Rainbow Dash looked over at her. "I thought this was a slumber party, not a science convention."

"Oh, yes! The party! How could I forget?" Twilight went towards the stairs. "Why should I be boring you with trivial facts and pointless figures that only apply to me? C'mon, everypony! Let's party!"

"Woohoo!" Pinkie cheered as she pulled out her Party Cannon and fired a blast of confetti into the air. "Let's get this party started!"

"Whoa!" Whisper stumbled back as he saw Pinkie pulling out the cannon and firing it into the air. "I never knew that Pinkie Pie was in possession of an illegal weapon..."

"I know it seems weird, Whisper, but Pinkie Pie's Party Cannon is not for any destructive purposes." Twilight walked up the stairs towards her room with the rest of the ponies in tow, now talking about all of the fun they were going to have. "And in case you're wondering, she did have to work hard for a permit to use that cannon in public."

"And when Twilight means hard, she wasn't kidding, Whisper!" Pinkie spoke to the space where Whisper was meant to be, but was invisible because no-one was looking through the lens. "So many papers..."

Everyone laughed at Pinkie's comment as they all made their way towards Twilight's bedroom for the festivities.

"Something tells me that this is going to be a long night..." Whisper followed the group, groaning about what the girls would be doing to pass the time, and for when the Boss Yo-kai attacked.

Later that evening, once the sun had disappeared behind the mountains and the moon had risen, the ponies were all together in Twilight's room, eating, drinking, and being merry. They knew that it was all going to be a hassle dealing with the Boss Yo-kai that evening, but that wouldn't stop them from having fun before the fight began.

The girls had been doing all sorts of activites and games. They did charades, roasted smores, wore facial masks made of mud and cucumbers, and even dressed up in clothes—much to Rainbow's dismay—to name a few. On the outside, they looked like they were having fun, when in reality, they were bracing themselves to face the Boss Yo-kai.

When everyone started to get tired, they all climbed into their respective beds in the main room. The layout was similar to the way they had organized it when the Tantabus had broken free of Luna's dreams, but now they had the Cutie Mark Crusaders sleeping with them.

"Now remember, Whisper." Twilight pulled the covers over her body. "The second you see the Boss Yo-kai, yell and scream at the top of your voice and wake me up. I'll use the Yo-Kai Watch EX and take it from there."

"Can do, Twilight!" Whisper saluted. "I'll make sure that that ruffian doesn't escape my sight!" And he began looking around with his hand still on his forehead.

"You sure that this is going to work, Twilight?" Applebloom asked as she cuddled up with Applejack in their bed.

"It has to, Applebloom." Twilight nodded at the filly. "If this Yo-kai isn't stopped, then it could go on to cat-ify Canterlot, the Crystal Empire, and maybe even ALL of Equestria!"

"What's so bad about being a cat anyways?" Pinkie Pie asked as she curled up into her bed. "Cats are pretty harmless—and incredibly fluffy-wuffy—pets. They're also super-duper cute, unlike those loud and noisy dogs—no offence, Applejack."

"None taken, Pinkie Pie." Applejack waved at her. "Winona has been a little bit feisty since ever since this whole hairball nonsense with Applebloom started this morning."

"Yes. And Opal quite literally scratched me across the face when I came to pick her up from Twilight's." Rarity leaned back and picked up her sleeping mask. "Which is why Twilight needs to fix this posthaste, before it's too late."

"Don't sweat it, Rarity." Rainbow Dash put her hooves behind her head as she and Scootaloo got comfortable. "Twilight'll handle this easily. She's come through for us many times before, hasn't she?"

"Yes. But against a giant cat who turns other ponies into cats?" Fluttershy nodded. "Twilight wouldn't dare try to fight if that monster tried using us against her..."

"Whisper's on full alert tonight, Fluttershy." Twilight assured as she tucked her in. "As soon as the Boss Yo-kai starts to inspirit you, he'll scream at the top of his lungs and wake me up." She showed her the Yo-Kai Watch just to be sure. "You should all get some rest now. I'll settle this."

Everyone else was apprehensive about going to sleep, but they eventually closed their eyes and dropped back into their pillows and headboards, snoring peacefully. As they began to dream their favourite things, they were soon lost in their own little worlds.

Twilight herself was the last one to go to sleep. She looked up at Whisper and said, "I'm counting on you, buddy. Don't let me down, OK?" before she too closed her eyes and drifted off.

Whisper watched Twilight sleep and began to wait for the Yo-kai to appear in the room. While the time passed, Whisper wondered how it would enter. He had a number of possibilities, like it showing up out of nowhere, climbing out from under the beds, or just coming right through the window.

He was taken aback when the Yo-kai slowly but surely opened the door and slinked through the tiny gap. It was then that he saw just who the criminal really was.

A massive cat, similar to the one that Opalescence had described was now walking into the room. It had a bushy tail, golden eyes, long white whiskers, sharp claws, and was licking its' lips as it looked down at the sleeping ponies. There was a symbol on its' belly looking like a cat standing on its' hind legs and calling for the moon.

"Well, well, well. Aren't you the sly ones, running away from me like that?" The cat spoke in a southern accent as it approached the guests of the slumber party. "Don't you know that your pony selves have been running yourselves ragged? I think it's time that you ditch the horsey side of you, and let your inner cat take over!"

"TWILIGHT! GET UP! GET UP!" Whisper shouted as the cat whipped its' tail at the other ponies, casting purple inspiriting flames on all of them. "THE BOSS YO-KAI IS HERE!"

Twilight immediately shot to life and activated her Yo-Kai Watch, switching it to the EX version as she scanned around for the Yo-kai. As she got a lock on the cat's position, she glanced over at her friends, who were now starting to glow the same colour as their coats.

All of Twilight's friends were being physically transformed. Their pony legs were replaced with cat legs and paws, their tails became short and bushy, their wings and horns disappeared, and their muzzles turned into cat faces, complete with small noses and whiskers. They were all purring like cats as the transformation went underway, and as soon as it was finished, the light dissipated as they all got out of bed and jumped towards the Boss Yo-kai, who had just been revealed by the Yo-Kai Watch.

"You!" Twilight jabbed a hoof at the giant cat. "Give me back my friends!"

"Sorry to cat and run, little horse, but I've got bigger fish to fry than deal with you!" The cat turned towards the door and charged through it, with Twilight's friends close behind.

"Hey! Get back here!" Twilight threw off the covers, grabbed her Yo-kai Medallium, and ran after the litter of cats as fast as she could. "Don't run away from me, you big, hairy freak!"

"Quickly now, my cat bretheren!" The Boss Yo-kai spoke to the cat pones who were running by its' side. "Disperse and make a feline for the cat playground! Make sure that this winged rat doesn't get to follow you!"

The cats meowed and split up around the castle, but Twilight was more focused on the big cat than she was her friends. She knew that as soon as the Boss Yo-kai was defeated, everything would return to normal, including her friends. She wouldn't waste her time playing a game that would make her miss her target.

Twilight was about to catch the Bos Yo-kai, when all of a sudden, two cats, who looked identical to Starlight Glimmer and Spike pounced on her and stomped on her back, causing her to crash to the ground and sprawl across the floor as they and the other cat-ified ponies ran out of the castle effortlessly.

"No!" Twilight slammed her hoof onto the ground as she watched the cats all escape and vanish into the night. She got back up and dusted herself off before she looked out of the open doors.

"Well, I'd certainly count that as moggy mayhem, wouldn't you agree?" Whisper helped Twilight get back onto her hooves.

"Not a good time, Whisper!" Twilight ran out of the castle. "We can still get them if we keep running. Just stay close to me, alright?"

"You're really commited to this, aren't you?" Whisper saw the fire in Twilight's eyes as she ran after the cats.

"Once I have a target, it doesn't get away!" Twilight shouted as she went into the town.

The chase then turned into a big game of hide-and-seek as Twilight looked around for the Boss Yo-kai and her cat-ified friends. She searched every trash can, every bush, every riverside, and even every litter box for any trace of her friends or the being that transformed them. Unfortunately, though, she had no luck.

Twilight gasped and panted for breath as she landed in an open spot in the town. She had checked everywhere where the cat ponies could have possibly been, but she had been completely unsuccessful in finding them. She stomped at the ground as hard as she could and cursed into the sky.

"DAMN YOU, GIANT CAT YO-KAI!" Twilight yelled as loud as she could, hearing her own words echo in the silence of the night. She looked down at her hooves, which were now trembling and sweating up a storm from all of the frantic searching and running she had been doing.

"There's no use in crying over spilt milk, Twilight." Whisper gently rubbed Twilight's back as she calmed down and steadied her breathing. "We lost the Boss Yo-kai, but, there may still be hope for us yet."

"Hope? What do you mean?" Twilight unsurely looked up at Whisper. "All of my friends are gone, and that giant cat is probably going for the rest of the world as we speak!"

"It's not gone yet." Whisper felt the air around him. "It's still cold out, meaning that the Boss Yo-kai isn't going anywhere soon. I'm not sure how it's possible, but I'm able to pick up Yo-kai auras of all kinds as soon as they come up. That's how I've been able to identify that there were smaller Yo-kai inspiriting your friends back when we first met, and the days after that."

"Huh? You're claiming that it might still be in Ponyville?" Twilight tilted her head sideways.

"Yes. There's an extremely powerful surge of Yo-kai energy in the Town Hall." Whisper pointed towards it and nodded his head. "I'm hazarding a guess that the Boss Yo-kai is in there. That, or a whole army of Yo-kai that you haven't met or befriended yet. One or the other."

"Then what are we waiting for? Let's go!" Twilight tried to move forward, but was stunned to know that she couldn't. Try as she might, her legs would not move at all. "Uhh, Whisper? Why can't I move?"

"Oh dear..." Whisper grimaced at Twilight's current condition. "I was afraid of this..."

The Yo-Kai Watch then projected a countdown from the number three, down to one. Massive drumbeats played as the numbers appeared, and with one big, louder crash of the drums, in addition to a symbol clang, the icon on the Yo-Kai Watch suddenly changed to show an angry red face with horns on a black background.

"Whisper! The picture on the watch just changed!" Twilight looked down at her watch.

"I hoped that this would've come when you made stronger Yo-kai friends. But I guess fate doesn't seem to play fair these days, does it?" Whisper looked at the icon on the watch. "You're going from the hunter to the hunted, my dear Twilight."

"Why? What's happening?" Twilight looked at Whisper hang his head. "Whisper! What's going on?!"

"Brace yourself, Twilight..." Whisper's voice became deep as he looked up at her with a serious look in his eyes. "It's Terror Time!"