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Neville Longbottom and the Hidden Swimming Pool

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This story is No. 2 in the series "I Know What We're Gonna Do Today!". You may wish to read the series introduction and the preceeding stories first.

Summary: One again, our intrepid inventors must discover a way to entertain themselves! Meanwhile, Neville discovers he's not seen the last of that troll from last year...

Categories Author Rating Chapters Words Recs Reviews Hits Published Updated Complete
Harry Potter > Non-BtVS/AtS Stories > Theme: Comedy
Cartoons > Phineas and Ferb
joshlamontFR1513,5473101,38819 Jul 1219 Jul 12Yes

NOTE: This chapter is rated FR13

Disclaimer: I neither own nor claim the rights to either Phineas and Ferb or Harry Potter.

...I had so many comments I was going to make, and now my mind's all blank. Er... I hope you enjoy this, and, uh... yeah! Clever comment!

“Man, this sucks,” Ron muttered, pulling out a bag of live gummy worms, “Everybody thinks I’m evil.”

“To be fair,” Harry said, patting his back, “You did build a giant mechanical dragon and had it attack the Forbidden Forrest.”

“Completely justified,” Ron replied immediately. “Did you see the size of those spiders?” He shuddered.

“Well, at least nobody thinks you’re the Heir of Slytherin,” Harry said comfortingly.

“Yeah, what’s up with that, anyway?” Ron asked, scratching his head. “The Heir is so obviously Malfoy!”

“We don’t actually know that, you know,” Harry said, putting the finishing touches on his automatic shaving ensemble. “It could just as easily be any of the Slytherins.”

“Next you’ll be saying it could be a Hufflepuff,” Ron muttered.

“Hullo, boys!” Hermione said, walking into the room. “Wot-cha’ do-in’?”

“Ron was just telling me how Malfoy has to be the Heir,” Harry replied cheerfully. “He made some pretty compelling points.”

“What, like how blondes have more fun?”

“What?” Harry blinked.

“What?” Hermione asked quickly.

Ron grinned. “Tones of evil overlord there, Hermione.”

“I do try,” Hermione said modestly, smoothing out her robes.

“It’s too bad there’s no way to prove he is the Heir,” Harry said, pulling out a book. “Genetic profiling wasn’t very common in Slytherin’s day.”

“Wellllll,” Hermione said innocently. “There is a highly dangerous and extremely volatile potion we could brew that would allow us to assume the identity of Draco’s friends and trick him into telling us.”

“That sounds like a great idea!” Harry exclaimed.

“Or we could just ask him,” Ron said, toasting his gummy worms over the fire.

“Huh. I guess that works, too!” Hermione shot a venomous glance at Ron. He was too busy watching his worms writhe to notice. “Come on, guys!”

Ron grumbled as Harry ran out the door, but shuffled to his feet and ran after Harry and Hermione. They quickly arrived at the Slytherin dungeons, and Harry knocked on the wall.

What?” Draco growled, yanking the secret entrance open.

“Do you know who the Heir of Slytherin is?” Harry asked.

Ha! As if I’d tell you, Potter! And what are you doing down here in the dungeons, anyway? You’re going to get in so much trouble if you don’t get out of here!”

“So, you don’t know?” Harry said.

GO AWAY.” Draco slammed the wall shut and went over to stick his head back in the fireplace. “So anyway, Blaise, I was walking into the common room, doing my usual saunter and mingle, when in walks Daphne Greengrass!”

“Are you serious?!”

“As a Black! Right there, in the same room!”

“Oh my wizard God!”

“I know! And then- Great Merlin, Blaise, you’re not going to believe this!”

“What? What happened?”

“She looked at me!”






“So what did you do?”

“Well, I walked up to her in a manly way- cautiously, you understand, one can’t be too careful about cooties- and then I, I flipped my hair, like this, and then I said…”

“What? What did you say?”


Get out!

“Huh,” Ron said as they began walking back, “I guess he wasn’t the Heir after all.”

“What makes you say that?” Hermione asked, hurrying to catch up.

“Draco would never pass up a chance to boast,” Harry said. “Or taunt us about knowing. He probably doesn’t have a clue.”

“Sooooo, I suppose we should be seeing about that potion?” Hermione asked hopefully. “To see if anybody else knows, I mean.”

“Nah,” Harry said. “Shapeshifting is cool and all, but those kinds of potions are tricky. What if you grabbed the wrong sample, or a cat hair got in or something?”

“…that would make for a lot of fetish fuel,” Ron said thoughtfully.

Hermione paled.

“Ron!” Harry exclaimed, “That’s brilliant! I know what we’re gonna do today!”

What?” Hermione shrieked.

“We’re gonna need smithy, several tons of sheet metal, a gurney, a medic- we can ask Neville for that- and… hey, where is Neville?”

----- Ne-villlllle!-----


Neville flew past all seven stories, the trick step on the moving staircase having vanished just as he put his foot down. He slammed intothe stone floor below, which turned out not to be a stone floor at all but actually a cleverly hidden swimming pool covered by one-way glass, and gargled desperately in the water. He blew out most of his air in a panic, but finally got a hold of himself and swam toward the only exit- a giant hatch guarded by stone trolls. Face turning purple, he managed to open the large steel door and swim through. The hatch closed behind him with a deep thoom, and a pump started up somewhere. Neville fell to the floor, gasping, as the water flowed out of the room.

agent n? agent n, are you there?” a muffled voice said.

Neville looked up.

agent n? you have to- Ahh, there you are, Agent N!”the voice exclaimed as Neville managed to wrench open the other hatch in the room. The troll from last year beamed from a giant mirror. “How’d you like our hidden swimming pool? Pretty clever, huh? The one-way glass was Hedwig’s idea, got it from the muggle world.

Hoot!” Hedwig hooted.

Neville cautiously made his way to the comfy armchair in the middle of the room.

We thought about throwing in some alligators, maybe a couple squid, but, you know, budget cuts. That shrimp doesn’t come from nowhere!

A shrimp cocktail popped into existence on a tray beside the armchair.

Want some? Dee-licious.” The troll held up a glass of his own. “Anyway, we’ve recently received intelligence that Voldemort is hanging out somewhere in the castle. We can’t tell exactly where because someone mistook the sand divination box as cat litter. I’m looking at you, Crookshanks!


Wha- that was only once!” The troll turned to Neville. “Ignore him, he’s been at the nip. Hey! You! Get off that vanity! No, that’s a priceless sixth century-

“Erm…” Neville hesitated. “Who are you people?”

The troll paused. “You mean they didn’t tell you at HQ? Good Lord! I knew things were going to get sloppy when Mr. Ed got promoted, but seriously!


No kidding? That’s terrible! Anyway, Agent N, Upton Uncial, at your service! Now go find Voldemort, and bring him down! Er, lower. Than he is. Oh, and you’re going to have to take the back way out. That one-way glass really only works one way.

----- Agent N! -----

“-reminded me of cosplay, and then I was thinking, who would wizards cosplay, muggles? But then it hit me! Gladiators! And so I present to you, the world’s very first Laser Colosseum!

Harry pulled the cord, and a vast canvas fell off to reveal an enormous three-story marble amphitheatre. The crowd roared.

“Thank you!” Harry waved. “Thank you! Now, don’t push, you all need to form a line and register at the entrance! Yes! Thank you! Here’s your laser sword, sir. And your laser axe, ma’am. Laser spear? Gotcha covered.”

Pansy walked up to the front of the line. “Got any laser whips, Potter?”

Harry shook his head. “Nope! Sorry, I just couldn’t get the light to bend like that. But how about this laser trident and net?”

“Is the net laser?”

“No, but it is electrified, though.”


“Imbued with lightning.”

“I’ll take it! Hey, Colin! Catch!”

It burns like the wrath of Thor!

Hermione stared. “Harry… did you just arm a bunch of kids with lightsabers?”

Harry beamed. “Yeah! Isn’t it neat?”

“Harry, that’s dangerous! A lightsaber will burn through practically everything but cortosis, and I don’t think we have any of that on Earth!

“Hermione, relax!” Harry said. “These are only training blades! Besides, I still have to hand out the shields!”

“The shields?” Hermione asked diffidently.

“Yup!” Harry pulled what seemed to be a giant mirror out of a box behind him. “See? The laser weapons’ll just bounce right off them.”

“Harry, you’re brilliant!” Hermione said, hugging him.

“So you want a weapon?” Harry said, pulling out of the hug.

“Do I ever!” Hermione lunged for the weapons bin.

Ron walked up to Harry. “D’ya think we should have told her we used Mestare crystals?”

“Nah,” Harry shrugged.

“So I said to him- what the hell is this?!” Draco exclaimed.

“We decided to build a laser colosseum!” Harry said. Hermione cackled as she ran by, twirling a pair of laser machetes. “See?”

“You getting in sooo much trouble for this, Potter!” Draco said gleefully. “They’ll expel you for bringing weapons to school!”

“What was that?” Harry asked, pulling up his visor. “Sorry, the helmet kinda clanged when I put it on.”

“I’m going to go tell the headmaster!” Draco shouted, running off.

“Oh, man!” Harry said worriedly. He turned to Ron. “We’d better start practicing. How much you wanna bet the headmaster learned to fight old school?”

“Hey, Harry!” Blaise said.

“Oh, hey, Blaise. Laser kampilan?”


-----Slytherin’sChamberOfSe-ecrets! -----

Eventually, Neville had stumbled across a pipe big enough to crawl through that actually seemed to be going somewhere. At least, there weren’t any more dead ends, and the pipe didn’t inexplicably spiral upward and then turn around on itself. And he could hear water up ahead so that meant something. Finally, he reached the end and pushed the hatch open.

“-and then I will FINALLY rule the ENTIRE UNI-TED KING-DOM! BWAHAHAHAhaaa?” The slightly evil looking young man spun around. “Who are you?” he blurted in shock. “How did you get down here? I thought I was the only one who discovered the entrance on the second floor in the girl’s lavatory!”

Neville blinked.

“Wha- I was not trying to take a peek! I just got a little disoriented. It had nothing to do with any sort of naked bodies! But anyway, it doesn’t matter and WHO ARE YOU?! What are you doing here?!”

Neville opened his mouth. “Never mind!” the boy interrupted, “Clearly you are here to stop me. You poor fool! What you did not know, Mr. New Guy, what you could not possibly imagine, is that you are standing before the Great- and Terrifying-” The boy threw out his hands. “LORD VOLDEMORT!

Neville gawked.

The boy frowned. “What? What? You don’t believe me? It’s true! I’ll show you!”

He whipped out his wand and began great giant letters in fire. “BEHOLD!” he cried, waving his wand. “THOMAS MAVOLOOR- MORVOLOO- MARV- wha? Excuse me a moment.” The boy discretely erased a letter and shifted a couple others over. “There. BEHOLD! THOMAS MARVOLO RIDDLE! (That’s my full name).” He tapped his wand on the letters and caused them to rearrange themselves. “I AM LOORD VOLDEMORT! LORD VOLDEMOORT! LORD- Oh, for Merlin’s sake, how does that O keep getting in there?”

He turned back to Neville. “Well, anyway, you see? YOU FACE THE FLIGHT FROM DEATH!”

He paused.

“That sounded a lot more impressive in my head.” The boy hrmphed. “No matter! What does matters is- I did it! You didn’t expect that, did you? That Voldemort himself could escape death? ‘Oooh, it’s impossible to do, Tom’, ‘No, Tom, you can’t mess with the natural order’, ‘Tom, where have you been, you’re covered grave dirt!’, WELL WHO’S COVERED IN GRAVEDIRT NOW?!”

Neville coughed.

Tom froze in his pacing. “Excuse me, I get a little worked up.” He adjusted his robes and smiled devilishly. “I’ll bet you want to know how I did it, ahh? Well, TOO BAD, I’m keeping it a secret! I will tell you how I came back, though. It was fiendishly eeeeevil plan that involved a diary, thirteen chickens, two silly girls, and the girl’s bathroom.” He glanced at Neville. “Not like that! I’m an evil overlord, not a pervert! Well, mostly not a pervert, I mean, you can’t say any guy’s not just little…” he trailed off. “Well, anyway! It all started years ago, when I a boy- an orphan boy. I’d love to move my feet; I’d hear a tune, and- you know what? I think this is best expressed in song.” He waved his wand.

The lights clanked out, and then a clacked onto Tom, who was bent over, holding his hat. A piano chord sounded.

When I was a boy- an orphan boy…


“GRY-FIN-DOR! GRY-FIN-DOR! GRY-FIN-DOR!” The western end of the colosseum roared with enthusiasm.

“SLY-THER-RIN! SLY-THER-RIN! SLY-THER-RIN!” The eastern end screamed back.

He-ey, you can’t fight! Your brains aren’t there, you troglodyte! He-ey, turn around! WHAM, oh, hey, brains’ on the ground!” Luna, it seemed, shared a bloodthirsty streak a mile wide with Hermione and managed to persuade the Ravenclaw hotties to ‘dress up for the occasion’, as it were.

BOOM-BOOM-CLAP. BOOM-BOOM-CLAP. BOOM-BOOM-CLAP.” The Hufflepuff crowd in the southern end didn’t speak. They just stomped on the ground in time, clapping in intervals. It was rather eerie, especially when they managed to do a twenty-four part clap/stomp/thwack that had four different beats in six alternating groups. Even more so when twelve Hufflepuffs separated from the groups and did the Dark Morris in between them all.

The arena below was a slaughter. Screams rent the air and bodies flew as light met flesh and shield met skull. Hermione herself was in the center, a whirlwind of blade and light. She chin-kneed Marcus Flint and then cut him off at the balls before using her mirror-shield to send him flying. “WHO WANTS SOME?” she screamed, letting loose a blood-curdling whoop. Daphne Greengrass responded in kind and came down from the sky with an enormous laser bastard sword. “Die, you torpid little pusillanimous swot! I come for your heart!

“So the snake wants to play, ah?” Hermione sneered. “Your heart isn’t worth the trouble, you ineffectual, loathsome little worm! I’ll take your ovaries!

“Hermione really seems to be getting in the spirit of things!” Harry said brightly.

“Though I think the ovaries line was a bit much,” Ron said, turning a bit green.

“Ah, they don’t really mean it!” Harry said.

Daphne slammed Hermione’s head into the wall and tried to gut her. The light made Hermione scream as it went through, but she brought her legs and kicked Daphne away, before head-butting her and bringing her machetes around in a flurry of lightning.

“Hm,” Harry said. “Okay, maybe they do have a little aggression to work out. But it looks like everyone else is having fun!”

The Hufflepuffs had somehow managed to break part of the walls down into rubble, and used that build themselves a fortress. The Ravenclaws, in turn, cut down trees from edge of the Forbidden Forest, hauled them in the colosseum, and were in the process of constructing trebuchets. The Slytherins (the ones that weren’t engaged in berserker brawls with the Gryffindors) were knifing both sides in the back.

“Yep, I think we can call this a qualified success!”

-----DunDunDun! -----

“So you see, Mr. New Guy, if only I had been allowed to express myself through dance, I wouldn’t have had to pour my soul into my diary!” Tom paused. “Though that kinda ended up making me immortal, so I guessed it all worked out, but STILL! I wasn’t even allowed to tap!

Neville’s eyes twitched.

“But I’ll get them back, just you wait and see! I’ll get them with-” He let off a giant hiss. “MY GIANT SLINKY! BAHAhahahahah!”

The ground rumbled, and then cracked and split open, and a colossal basilisk rose up behind Tom Riddle.

“NOW WHO’S NOT ALLOWED TO TAP?” Tom cackled. “With this, my biological turn-to-stoneinator, I shall freeze every dancing nazi in the entire United Kingdom!” He paused. “And possibly Spain, I don’t like that crazy jiggly dance they do down there. “ He turned and hissed at the wall. It rumbled behind before slowly grinding open. “GO! GO! Wreak havoc on those that would oppose us! Find the beat of the drum in our blood, my pet!”

The basilisk lurched out of the chamber and into the pipe behind the wall that Tom Riddle opened, leaving just Neville and the Boy-Who-Would-Be-Overlord.

“Now, what to do about you?” Tom asked. “Hm.” He tapped himself. “Almost solid!” He walked over to what Neville had thought was a bundle of clothes, and rolled it over to reveal a young girl. “Looks like she’s about finished, too.” He glanced up. “Oh, oh this? I’m just drinking her in.”

Neville recoiled.

“Wha- I told you, it’s not like that, geez! I’m using her life to power mine. I-it all stems from the diary, you see? She writes in it to me, and then I pull her life out through- you know what, why am I explaining this to you, it’s all very technical and you don’t look like you can even understand simple multidimensional psychokinetic conversions. Really, I don't know...”

As Tom rambled, Neville’s eyes darted around the girl. Tom said her soul went through a diary, that meant it had to be- there! He ran over as quietly as possible for a boy with soggy shoes.

“-and that’s why we need to hire more gypsies!” Tom stopped and looked around. “Where did he go? Wait- don’t touch that!” Tom screamed as Neville picked up the diary. “Oh, no, no, you’re going to get it all wet and-” Tom started flaking. “Wait, what’s happening? What did you put in that water?” He sniffed the air. “Chlorine? You’re soaking my diary with chlorine? You’re bleaching my pages?! Nooooooooooo!” Tom screamed as he began to decompose. “Curse you, Mr. New Guy! Curse youuuuuu!


“Have at thee, knave!” Harry cried, brandishing his lights-*ahem* laser sword. “I shall- huh?”

The ground rumbled for a second time that day, and then burst open as a basilisk rose above the colosseum.

“Dragon- SHIELDS!” Harry bellowed, and every person on the battlefield lifted their mirror-covered shields into the air. The basilisk roared and snapped its head down when it saw another basilisk, but it was too late- its image had already been reflected back, and it turned to stone.

“What the bloody hell was that?!” Ron shouted.

“I dunno…” Harry said as the basilisk teetered. “But it looks like it’s coming down! EVERYBODY RUN!”

The students screamed as the basilisk fell, scattering out the colosseum in every direction. The giant snake crashed into the enormous building, pushing it forward and into the lake, where it sank along with the basilisk.

Hermione wept. “All our weapons- our shields- my machetes, were in that stadium.”

“There, there, Hermione,” Harry said, rubbing her back. “There’s always your pair at home.”

“That’s true,” Hermione admitted, wiping her eyes.

“There they are, headmaster!” Draco’s voice exclaimed. “Right over here! You should see them! Fighting with all sorts of swords and knives, and I bet there’s even some muggle gonnes!”

“I very much doubt that, Mr. Malfoy,” Dumbledore’s voice replied. “Even if they could get that black powder to burn, I don’t believe any of my students would be so irresponsible as to-” They crested over the hill. “Well. It appears I was right.”

What? Look!” Draco demanded.

“I am looking. Hello, children. What are you all doing here?”

Harry shrugged. “We were doing a little historical reenactment, but then we lost our stuff in the lake.”

“One of the dangers in playing around water,” Dumbledore said gravely. “I do trust you all were careful and nobody other than your props was hurt?”

Harry wiggled his hand. “Give or take. Some of the girls really got into it.”

“Well, injuries aside, that’s wonderful to hear. It seems so very rare to see anyone get interested in history anymore.”

“But- but- but-” Draco stammered. “It was here. It was really here, for real this time! What did you do, Potter? Is it under some sort of invisibility cloak?”

Dumbledore sighed. “Mr. Malfoy, there is no such thing as an invisibility cloak, especially not for something as large as you described. Perhaps you should accompany me to see Madame Pomfrey.”

“But, but, but…”

“Hey, Potter,” Daphne said, walking up. “Cool stadium. I guess you Gryffs aren’t all talk.”

“I’m glad to hear it!” Harry said happily.

“Granger,” Daphne nodded. “Good fight. We should try again sometime. You know any other styles?”

“Oh, bring it on, Greengrass!” Hermione grinned viciously. “I know more than you can even imagine.”

Daphne’s lips curled into a shark-like grin. “Good.” Her face suddenly lost all expression. “Oh. Hello, Longbottom.”

“Oh, hey, Neville!” Harry exclaimed. “Whoa. You got caught in the splash?”

“Had to find my way out of a pipe,” Neville gasped.

“Oh, man, rough,” Harry said. “Come on, let’s get you to the common room. Coming Ron?”

“Of course,” Ron said, trudging up behind them. “Hey, Neville, did you see any Italians down there? I heard something about a plumber who never got out…”

To bed!

The End

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