Just before Ash's semi-final battle, Paul came up to him.

"So you know, I'm your opponent for this one," he said.

"Yeah, I checked who the top eight were," Ash agreed. "I didn't recognize some of the names, but I recognized yours, so I guessed we'd end up battling one another."

Paul blinked. "Why?"

"Your Pokémon are strong, that's why," Ash replied. "I don't agree with how you train some of them, but they trust you and believe in you."

The other trainer gave Ash a long look, then turned to look at Pikachu instead.

"That's the best explanation I'm going to get, isn't it?" he asked.

Pikachu twitched his ears. "Honestly, he's a bit more positive about it than I'd be – but he's got a point. You are a solid trainer."

"I'm going to assume that that would have been meaningful if I understood it," Paul decided. "But what I wanted to say was… I'm not going to ask you to use your strongest Pokémon, because I'm not sure what that would look like and I'm vaguely worried you'd bring out Arceus and… some Pokémon I've never even heard of. But I don't want you to take it easy on me, either."

"Don't worry about that!" Ash told Paul. "I already know the team I plan to use, and it's a good fit for what you want!"

"Which would be true of just about anyone in your collection," Pikachu opined.

"So… you're not actually one of Ash's Pokémon?" Lucian said, wanting to be sure of that.

"Correct," Zygarde confirmed. "He has never asked, and I have never offered, so I have not had to consider what my answer would be if he did ask. Instead I am having a lift back to Kalos."

"Ash doesn't have a Pokémon who can get you back to Kalos quickly?" Lucian asked.

"Oh, he does," the Dragon-type said. "I simply prefer to take the scenic route. I met him in Johto."

Lucian glanced off into the distance for a moment, then shook his head.

"That's a very scenic route," he decided. "Are there any other Pokémon who are just following Ash around?"

"There's Marshadow, but he mostly hangs out in Ash's shadow," Dawn said. "He's got a great collection of snack foods in there, actually."

Cynthia looked interested. "What kinds?"

"That is not the most important thing here," Flint said. "Hey, look, they're sending out their first Pokémon!"

Paul began with his Ursaring, a big burly Normal-type that rolled his shoulders and looked across at Ash's choice.

Ash's choice, which had been in an orange-topped Pokéball instead of the usual red. And which appeared very much to be a tiny Pikachu.

"Shuffle!" Ash called, and the tiny Pikachu turned into a tiny and unfamiliar Pokémon.

"Oh, so that's what they looked like," Whitney's Stantler said, and evolved into a Wyrdeer. "I've been trying to find that out for decades."

"Query," Zygarde said. "Is that why you have been along?"

"It is one reason," Wyrdeer confirmed. "Initially the only reason, but that changed within about three minutes."

Paul frowned. "Ursaring, close your eyes. That Pokémon's using too many illusions, you can't trust them."

Ursaring promptly did close his eyes, and the weird Pokémon – seemingly – cantered around in a circle for a long moment before shooting a beam of psychic energy at Ursaring.

"Now, Charge Beam!" Ash said. "Power yourself up!"

Paul clenched his jaw, then forced himself to relax.

He needed to concentrate. Battling a Pokémon that used illusions like this was hard, but… all he really needed to do was be sure where the other Pokémon was.

Or… did he?

"Ursaring," he said. "Earthquake!"

The ground jumped as Ursaring slammed his fist into it, ripping the ground up in a rippling wave that knocked Ash's Pokémon into the air.

"Keep it up," Paul said. "Use Earthquake again."

He finally had something that worked, and-

"Shuffle!" Ash called.

The strange cervine Pokémon turned into a tiny Palpitoad.

"Shuffle again!" Ash said, this time getting a tiny Wailord that averaged out as being quite big. "Waterspout!"

Paul rubbed his temples.

Now he was going to have to come up with another new plan.

"Open your eyes again, Ursaring," he said. "I don't think this one is illusions… Giga Impact!"

"So what is this one, then?" Cynthia asked. "Another Zorua?"

"Actually, he's a Ditto!" Mew explained. "He's Ash's Pokédex, but obviously that means knowing about all the Pokémon because otherwise he wouldn't be able to explain what he runs into. He's called Ibid."

Byron laughed.

"Good one," he said. "I like that, it works on multiple levels."

"So does Ibid, if he's a Pokémon with Fly or Levitate," Mew replied.

"But why are they all small?" Cynthia said.

"Why not?" Whitney asked. "There's no Pokémon that can't be improved by being smaller, with the possible exception of the ones which were only just big enough to give a nice hug because then you might lose the huggability. And I suppose the really really small ones already like Joltik, because then you can't see them at a distance."

"I'm not really disputing that," Cynthia said, smiling. "I mean something more along the lines of wondering why they're small. Is there any reason, Mew?"

"There is!" Mew concurred. "It's because Ibid's a small Ditto."

"But…" Flint began. "I'm not sure how that would mean that anything he turned into would be small."

"Because when a normal Ditto turns into something then it turns into a normal sized version of that thing," Mew replied. "Therefore, when a small Ditto turns into something then it turns into a small version of that thing. Simple!"

"It really isn't," Flint grumbled.

Several minutes later, Ash and Paul were having a basic-Pokemon versus final-evolution match.

"Wait," Paul said, firmly, as Turtwig activated Overgrowth. "I don't know how he's doing that, but wait…"

Torterra rumbled something about how that was easy for him to say, but complied readily and shifted his footing a little to steady himself.

"Shell Smash!" Turtwig added, and Paul pointed.

"Now," he said. "Stone Edge."

A hail of rocks came slamming out from Torterra towards Ash's Turtwig, and the Grass-type flicked to the side to avoid one attack only to be hit by the second wave of stones. That knocked him stumbling backwards a little, setting him up for a direct hit, but the third one bounced off his twig and didn't do any actual damage.

"Earthquake," Paul followed up. "I know he's resistant but it's still a powerful attack… now, Hyper Beam."

"Shell Trap, Turtwig!" Ash called. "Use the blast as a shield!"

The Hyper Beam hit Turtwig before Ash finished his explanation, but one of the good things about the plan was that Turtwig didn't really need to be aiming to do it for it to work anyway. The explosion negated a lot of the force of Torterra's assault, but it still sent Turtwig sliding back several feet, and the Grass-type shook himself out when he got to his feet.

"I can see I need to be serious," he said. "I'm going to have to go up another gear."

He took a deep breath, then clenched his muzzle shut and his twig twitched.

Another breath in, and this time his twig inflated until it was four times as tall as the rest of him put together and trembled slightly in the breeze. Then the whole of Turtwig got bigger, and he began lumbering towards Torterra.

"What on earth are you doing?" Torterra asked. "Is that Growth? Why is that like that?"

"Huh?" Turtwig replied, before swinging his twig as a Wood Hammer and knocking Torterra sideways. "Haven't you heard of a rubber tree?"

"You should be floating away!" Torterra complained, throwing a Stone Edge attack which bounced off Turtwig with a loud boing.

"But I'm not using Fly," Turtwig replied. "And I don't have the Levitate ability."

"Bullet Punch!" Ash called.

Turtwig used Bullet Punch while Paul was still trying to work out what was going on.

Back at Oak Ranch, Torkoal groaned.

"My student has done it again," he said, turning to face Grovyle. "I'm very pleased by how he's a Genius of Hard Work, but sometimes I feel like he hasn't quite got which Shonen Jump series we're supposed to be doing."

Grovyle looked up from fiddling with a Leaf Shuriken. "Huh? You say something?"

Torkoal hissed like a tea kettle. "So cool…"

"Thunderbolt!" Paul ordered.

"Psycho Cut!" Ash countered, and Articuno flicked up her wing and sliced the bolt of lightning in half. The two halves flicked wildly away, earthing themselves on the ground again with a fzaaap, and Paul frowned.

"Thunderblast," he decided.

The Electric-type's tails slammed into the ground, sending up sparks, and he blasted away at the ground with Thunder to blow some rocks into the air. His tails flicked to send the rocks towards Articuno, but she sliced them apart with her wings as well.

"Are you going to do anything apart from just hover there and defend?" Paul asked.

"Aaar," Articuno checked, glancing back at Ash.

"Sure!" Ash agreed. "Mystical Fire!"

Articuno swiped both wings, this time, and somehow – Paul wasn't quite sure how – the friction of her wings rubbing on the air sent a trail of flame and sparks through the air, which turned into a coiling wave of flame darting down towards the Electric-type.

Electivire counterattacked with a Thunderbolt, which knocked one flame streamer aside, then used Brick Break as the next part of the attack reached him. That actually worked, a little, but then Articuno transfixed Electivire with a very stern glare and Electivire froze in place.

There was ice, and everything.

Paul glanced up at the board, which showed five Pokémon eliminated on his side and Electivire as his only Pokémon left.

He clenched his fist, thinking about how he was going to get out of this, then sighed.

There was no choice.

"Electivire!" he called. "Don't give up! You can do it – just a bit more effort!"

Articuno hovered overhead, and after a long moment nothing had happened.

Then Electivire twitched.

Electrical energy surged through his arms and fists, rapidly heating them up to a glow, and Electivire used Fire Punch – exploding out of the ice, lashing up, and hitting Articuno in the wing.

Ow! she yelped, telepathically, and Electivire followed up with a Thunderpunch. Then Articuno used Extrasensory, ramming the Electric-type back into the ground, but he wasn't out yet and began using the Thunderblast trick again.

"Oh no, it works," Paul said, very quietly.

But at the same time… it felt good. Ash still had two Pokémon left after Articuno, so he didn't think he was going to win this battle, but he knew he was giving Ash a lot of trouble and that was something to be proud of.

AN:

Yep, that's the official full explanation of Ibid.