"Alola, challenger," Kahuna Hala said, then actually noticed who he was talking to. "Ash Ketchum?"

"That's me!" Ash agreed. "Hi!"

He waved. So did Pikachu, and Zygarde, and Rowlet sleepily waved a wing from where he was perched on top of Ash's head for better sunlight.

Rotom made a hand emoji appear on his screen, and wiggled back and forth a bit.

"So, what brings you here?" Hala asked. "Here to do the Island Challenge? Because, I'll be honest, I might need a bit more warning for something like that."

"Not really," Ash replied. "I was more asking you for some help with figuring something out. Professor Kukui wants to know what I find out about Z moves, and I've got a couple of Z-crystals, so I thought I'd see if you could help make sure I'm doing it right!"

Hala frowned slightly. "You've got a Z-ring?" he asked. "If you don't have one, you'll need one, and that does mean doing the challenge."

"Yeah, I've got one," Ash said, showing it off. "It came with what I think is an Electric-type Z-crystal, and then I got a Grass-type one from Gumshoos earlier. They said it had something extra."

"Well, that could mean anything," Hala frowned. "Can I have a closer look at that Z-ring?"

Ash handed it over, and Hala turned the Z-ring around before nodding.

"Yes, I thought so," he said, looking up and fixing Ash with a frown. "Where did you get this?"

"Tapu Koko threw it through Professor Kukui's window last week!" Ash replied. "Then he ran away."

"Well, that does explain the mystery of where this one went," Hala decided. "I make Z-rings, and one of them went missing a week or so ago. That's this one. Still, if one of the Tapu decided you should have it I'm not going to argue."

He straightened up. "Now. What do you know about Z-moves?"

"I've seen them a few times," Ash said. "Mostly when Gary used them on me, and I did Mew's special one once. How do you tell what pose goes with what Z-move?"

"That's actually what I was getting at," Hala replied. "So, the basic idea behind a Z-move is…"

He trailed off. "Mew has a special Z-move?"

"Yep!" Mew agreed, appearing with a pop. "It's called Genesis Supernova! It's a big explosion!"

"When I did that one, I just knew what to do, but there was a bit of a time loop involved," Ash clarified. "Or a predestination paradox, I don't know which one offhand, Dawn and Pichu know the exact wording… anyway, I've done that one, but if I wanted to use one of the other ones, how would I do it?"

"Well," Hala said, deciding to go back to what he was about to say. "A Z-move is made out of a normal move, just making it stronger. That can mean any move of a specific Type, or for the special Z crystals unique to certain Pokemon it can mean a particular move."

"Oh, okay!" Ash said. "And the poses… I guess if you're properly synced up with your Pokémon they just come to you, right? Rowlet, want to give it a go with the Grass one?"

Rowlet made a snoring noise.

"I guess we'll let him sleep," Ash decided. "Meganium, you're the other one who helped win this, so let's try it out!"

"Are you sure that's a good target?" Hala asked.

"Yeah, it'll be fine," Ash replied. "The GS Ball's been through a lot with me, it's indestructible!"

Hala looked again at the gold-silver Pokéball propped up on a sizable rock, then decided not to press the issue.

"Since Meganium is a four legged Pokémon," he began, "the poses work differently."

"I guess it's because if you have a Pokémon who can't do the pose, it still works, but if your Pokémon can do the pose they at least have to try, right?" Ash asked. "Because not doing something because you can't is way different from not doing something because you can't be bothered."

"...yes, actually," Hala confirmed. "I should really stop being surprised when you jump ahead like that."

"That's Ash for you," Pikachu said, not that Hala could understand but the sentiment came across.

"The pose is different for each type," Hala resumed. "Not for each move. There might be a couple of exceptions, but for example the pose for Shattered Psyche is like this."

He struck a pose, and Mew brightened. "That's the one Ash did when I blew up the time vortex!"

"Let's try this, then, Meganium!" Ash said. "What's the Grass pose?"

Hala raised his arms, and Ash copied him.

Then Meganium opened her petals fully, gathering sunlight, and brilliant energy surrounded them both.

"I don't know what, but something is vaguely familiar-" Mew began.

"What just happened to your crystal?" Hala asked.

"Huh?" Ash said, but then a blast of intense light slammed down from directly overhead onto the GS Ball. It shone so brightly that everyone except Meganium either flinched away or yelped in shock, and when it faded the rock had lost about an inch of surface everywhere except directly underneath the GS Ball.

And there was a riot of greenery around the base of the rock, where the grass that was already there had grown by at least a foot.

"That was not Bloom Doom," Hala declared.

"I have no data on this!" Rotom announced. "I have a recording, though, which means that I now have data!"

Ash looked down at his Grassium Z, which wasn't a Grassium Z any more. Instead of a diamond it had a six-petal shape, and the leaf had been replaced by a pair of antennae.

"Oooh!" Mew gasped, as Meganium panted for breath. "That must have been a special Meganium-exclusive Z move! Like a really supercharged Solarbeam… hmm… Solar Flare? That sounds like a good name!"

"I hope you don't make a habit of this," the Kahuna said. "Or, if you do, the crystals at least turn back again. We don't actually have all that many of them."

"That was really cool!" Ash said. "...wait. Meganium, I guess you're tired, right? I heard Z moves do that… but once you're rested, maybe tomorrow, we should try having you Mega Evolve and do that! Let's see if we end up with a Mega Meganiumnium Z!"

"I want to file a complaint," Rotom said. "I do not know who to, but I know there's probably someone."

"Running BlameSearch app," Arc provided helpfully.

"Results returned," Arc said.

"Huh?" Ash asked.

"BlameSearch completed," Arc explained. "From yesterday. It turns out that BlameSearch takes an extremely long time to conclude."

They made a disappointed beep noise. "Unfortunately it also runs a root cause analysis. This means that all BlameSearch results can be traced back to Arceus and Mew at the same time. Deleting BlameSearch App."

"Huh, that's not great," Ash admitted. "Are you going to do anything else?"

"I am not," Arc told him. "I would like to send a message to whoever created the app, but I have no viable way of determining who that is."

Ash thought about that, then shrugged.

"Well, anyway!" he said. "Okay, class, it's time for another lesson about physics! This time it's about a different thing, which is momentum. Who can tell me what momentum is?"

Lillie was the first to answer, this time. "It's how hard it is to stop you."

"That's a great answer!" Ash agreed. "It's how hard it is to stop you, and it's also how hard you can shove someone else. It's different from how hard you're hitting someone, though, that's energy."

He waved his hands. "So, a really fast small thing can still make a big crater, or do a lot of damage, because it's got a lot of energy, but it's much harder for it to push something backwards. Something that's heavier can be moving slower, so it has less energy, but still have more momentum… let's show some examples!"

Ash sent out Cresselia, who waved, then Pidgey.

"So, this is Cresselia!" he introduced. "She's a big Pokémon – a heavy Pokémon, really, but I'm saying big because otherwise it sounds a bit unpleasant – so it takes a lot of work to give her momentum, and she's also really tough. And this is Pidgey, she's much smaller and lighter so she's got less momentum. Which means that when Pidgey battles, she can move around a lot, but her hits aren't all that hard – she can dodge a lot!"

Pidgey began demonstrating, zipping past in one direction and then turning to go in the other direction.

"Small Pokémon have to rely either on hitting really fast, or on using attacks that don't rely on speed so much," Ash explained. "Which is to do with momentum. But if you've got a bigger Pokémon…"

Pidgey flashed white and turned into Pidgeotto.

"Whoa!" Kiawe said. "Did you plan that?"

"Yeah?" Ash replied. "Why? It's part of the lesson."

"How do you train a Pidgey to evolve on command, that's amazing," Mallow breathed.

"Pidgeotto can just evolve in both directions, that's all," Ash shrugged. "But watch, because Pidgeotto's bigger now and so she's got more momentum. It means she's got to do more work to make the same kind of turns, but it also means that if she hits a Pokémon at the same speed it hits harder and shoves them back more. Ready, Cresselia?"

Cresselia nodded.

"Quick Attack!" Ash called, and Pidgeotto slammed into Cresselia. The impact sent the floating Psychic-type backwards a bit, before she slewed to a halt and moved back to where she'd started.

"So Pidgeotto's attack hit quite hard, because of how fast she was going, but it also moved Cresselia backwards a bit," Ash pointed out. "That's momentum. Now, Pidgeot, Quick Attack!"

Pidgeot hit Cresselia, as well, and this time drove Cresselia back a lot further.

"Error!" Rotom said. "My data indicates Pidgeot is only a bit heavier than Pidgeotto. Explain?"

"Oh, yeah, someone told me this once," Ash said. "They only measure one Pokémon to get how heavy it is, and sometimes they don't get it right. Pidgeot's a lot bigger than Pidgeotto, which is why she's that much heavier… by the time you've got a Pokémon like Pidgeot, or another big one, they've got a lot more momentum so it's harder for them to steer. And they hit a lot harder, but it's harder for them to score hits like that. Thanks, Pidgeot!"

Pidgeot reverted back to Pidgey, and landed on Ash's arm.

"Now, what about a Zorua or Zoroark?" Ash asked. "How do you think a Pokémon like that could use what we've already talked about?"

"I guess they could pick if they're being heavy or light?" Lana guessed, uncertainly. "Is that something they can do?"

"Right!" Ash agreed. "And because of that, a Zorua can turn into a light Pokémon to change course and then a heavy Pokémon to hit. It means it breaks their illusion when they hit, but it's a great trick to use, especially because they can also turn into a heavy Pokémon to not be knocked around. What about a Rhyhorn?"

"They're heavy, so they've got a lot of momentum, and it's hard to knock them about," Sophocles said. "And when they charge, they hit hard."

Ash gave him a thumbs-up. "What about Cutiefly?"

"Really light," Lillie said. "They need to watch out for it."

"And Snorlax?"

"They're super hard to move!" Kiawe said. "I get it, so a Snorlax doesn't need to worry about being hit by a light Pokémon much at all, at least not from momentum and stuff."

"That's true!" Ash said, sending his out. "But there's something else, too."

Cresselia checked a map, then slid sideways a bit. "I'll bring back a souvenir from Poni."

"Snorlax, Extremespeed!" Ash ordered, and Cresselia was abruptly replaced by Snorlax. There was a faint sort of blur in the distance for a moment, though.

"See, if a heavy Pokémon like Snorlax is moving really fast, they have so much momentum they can knock another Pokémon a really, really long way," Ash concluded. "That can be helpful for all kinds of reasons!"

AN:

Because of course I had to use the term Mega Meganiumnium Z. I've been planning that since Whitney's gym.