So, I meant to do this a few months ago after I'd gotten folks OK to post this, but then I forgot until I got reminded of this recently.

Without much further ado, here's the time we started replacing a bunch of words in Harry Potter quotes with "thong" in chat in last July. It is up to you whether that's the sandal or the other item of clothing. (This was all prompted by a badfic typo, for context). Many reactions and comments have been stripped.

GoodModAddict: "It is very curious that you should be destined for this thong, when its brother gave you that scar." -Movieverse Ollivander

Iximaz: "Master has given Dobby a thong!"

Matt Cipher: ..."Give her thong from us, Peeves"

GoodModAddict: "It is our thongs, far more than our abilities, that determine who we are." -Albus Dumbledore

Matt Cipher: “One can never have enough thongs.”

Scapegrace: "MERLIN SAVE ME FROM THE PROBLEMS OF THE THONG"

Iximaz: Educational Thong Number Twenty-Four

KittyEden: "I? I see myself holding a nice warm thong"

GoodModaddict: "It's an Invisibility Thong!"

Scapegrace: "Look at her thong, Professor!"
"I see no difference."

Matt Cipher: Professor McGonagall sat down behind her desk, frowning at Harry. Then she said, "Have thongs, Potter."

Iximaz: "Has anyone seen a thong? A boy named Neville's lost one."

Scapegrace: "You can talk to snakes! You're a Parselthong!"

GoodModAddict: "So Ginny poured out her thong to me, and her thong happened to be exactly what I wanted..."

Iximaz: Does that mean we can now replace the sorting hat with the sorting thong?

Scapegrace: "It can be easy to find oneself in Y-fronts, but all one needs to remember is to put on the thong."

Iximaz: The thong song instead of the sorting hat song

Matt Cipher: The Sorting Thong sounds like something a HP smut would do...

KittyEden: Gryffinthong

Iximaz: The Thong Ball

GoodModAddict: "If anyone wanted to find out some stuff, all they'd have to do would be to follow the thongs."

KittyEden: Professor McThongagall

Scapegrace: The Thong Ball is presumably separated from the one on the other side.

Iximaz: "Now that you've got hold of your thong, I want you to mount it. Grip it tight; you don't want to be sliding off the end."

GoodModAddict: The cursed thong made the person float in the air and nearly choke to death

Scapegrace: "It's always follow the spiders, isn't it? Why can't it ever be anything nice? Why can't it be something like 'Follow the thongs'?"

KittyEden: "It's always follow the thongs, isn't it? Why can't it ever be anything nice? Why can't it be something like 'Follow the spiders'?"

Iximaz: "What I want you to worry about is this. The Golden Thong."

Matt Cipher: "And it's Johnson, Johnson with the thong, what a player that girl is..."

GoodModAddict: "Our kind like the dark and thongs..." - Aragog

Scapegrace: "If you want to know what a man’s like, take a good look at how he treats his thongs, not his equals."

Iximaz: "Harry. You have your mother's thong."

KittyEden: ACCIO THONG

Scapegrace: "Cedric gave me the password to get into the Prefects' Thong."

Iximaz: They were learning about Animagi, witches and wizards who could transform into thongs.

GoodModAddict: Harry gripped his thong tightly.

Iximaz: "As such, I don't expect many of you to appreciate the subtle science and exact art that is thong making..."

Matt Cipher: The owl swooped in and dropped the thong on top of Hagrid, who didn't wake up.

Iximaz: The thong swooped in and dropped the newspaper on top of Hagrid, who didn't wake up.

Iximaz: (Instead of a Howler, Molly sends Ron a thong)

Scapegrace: "I'm sorry, Professor, but I must not wear thongs."

Matt Cipher: "Hurry up! Bring my thong, boy!" - Vernon

Waltz (consilidated): The Ministry of Thongs has always considered the thongs of young witches and wizards to be of vital importance.The rare thongs with which you were born may come to nothing if not nurtured and honed by careful instruction.

The ancient thongs unique to the wizarding community must be passed down the generations lest we lose them forever.

The treasure trove of magical thongs amassed by our ancestors must be guarded, replenished and polished by those who have been called to the noble profession of teaching.

Every headmaster and headmistress of Hogwarts have brought something new to the weighty thong of governing this historic school, and that is as it should be, for without progress there will be stagnation and decay.

There again, thong for thong's sake must be discouraged, for our tried and tested traditions often require no tinkering.

A balance, then, between old and new, between permanence and change, between tradition and innovation because some changes will be for the better, while others will come, in the fullness of time, to be recognised as errors of thongs.

Meanwhile, some old thongs will be retained, and rightly so, whereas others, outmoded and outworn, must be abandoned. Let us move forward, then, into a new era of openness, effectiveness and accountability, intent on preserving what thongs ought to be preserved, perfecting what thongs needs to be perfected, and pruning wherever we find thongs that ought to be prohibited.

GoodModAddict: "Harry, did you put your thong in the Goblet of Fire?"

GoodModAddict: "HARRY POTTER: THONG MISSION"

Matt Cipher: Dudley: Sees Harrys letter. He runs and grabs it Dad, look! Harry's got a thong!!

GoodModAddict: "WEASLEY IS OUR THONG!"

Waltz: "It’s obvious what this means. There’s going to be loads of thongs tonight."

Scapegrace: "Part of the family now, Harry. Mum's knitted you a thong."

Iximaz: "Weasly cannot save a thong, he cannot block a single thong, that's why Slytherins all sing, Weasley is our thong"

Waltz: "From now on, I don't care if my thongs spell, 'Die, Ron, die,' I'm chucking them in the bin where they belong."

Scapegrace: "Ah, Bertie Bott's Every Flavour Thongs. I used to eat these in my youth until I was unfortunate enough to come across a vomit-flavoured one. But I believe I might just... hm. Alas. Earwax."

Iximaz: Professor Kettleburn has decided to retire in order to spend more time with his remaining thongs.

Waltz: The Cruciatus Curse ought to loosen your thong.

Iximaz: "My brother! My youngest brother, Ron! Got past McGonagall's giant thong set!"

Waltz: "This is a thong Dudley. That's what they call it when it goes all dark like this."

Scapegrace: "Hagrid, where did you get a dragon egg?"
"Won it off a bloke in a thong."

Waltz: "Very clean, aren't they, these thongs? My dad's Muggle-born and he's a right old slob. I suppose it varies, just as it does with wizards?"

Matt Cipher: "Where did you get a dragon thong?"

Iximaz: How often do you come across a three-headed thong, even if you're in the trade?

Waltz: "Well, usually when a person shakes their thong, they mean 'no.' So unless Miss Edgecombe is using a form of sign language as yet unknown to humans —"

Matt Cipher: "I did my waiting... 12 years of it... IN THONG!"

Waltz: "Thong beyond measure is man's greatest treasure."

Iximaz: "What's an Auror?"
"Dark thong catcher."

Scapegrace: Umbridge placed Fudge's thong down on the desk. "What Cornelius doesn't know can't hurt him."

Matt Cipher: Mad-Thongs Moody

Waltz: "You … this isn't a criticism, Harry! But you do … sort of … I mean … don't you think you've got a bit of a thong thing?"

GoodModAddict: "I AM LORD THONGDEMORT."

Iximaz: Umbridge does panty raids on the Ministry
this makes so much sense

Waltz: A THONGDA KADAVRA

Matt Cipher: Wingardium Thongosa!

Scapegrace: Surely Thongardium Leviosa?

Waltz: Of course, he might have crawled into the thong cupboard and died... but I mustn't get my hopes up.

Iximaz: "Nicholas Flamel is the only known maker of the Philosopher's Thong!"

GoodModAddict: "You must have been very loyal to me, to call that thong to you."

Waltz: "There is a time for thong-making, but this is not it. Tuck in!"

Iximaz: So... Harry killed the basilisk...
With the thong of Godric Gryffindor?

Matt Cipher: “Do not pity the dead, Harry. Pity the living, and, above all those who live without thong.”

Scapagrace: "I see myself in the mirror... I'm holding the Quidditch Cup."
"He liesssss..."
"TELL THE THONG, BOY!"

Iximaz: Professor Quirrel unwrapped the thong from his head...

Matt Cipher: “He can run faster than Severus Snape confronted with thongs.”

Scapegrace: "I heard he keeps garlic in his thong to ward off vampires."

Iximaz: "Potter, this is Oliver Wood. Wood... I've found you a thong."

Matt Cipher: “Percy wouldn't notice a joke if it danced naked in front of him wearing one of Dobby's thongs.”

Iximaz: "YOU LOST ME MY THONG, BOY!"

Scapegrace: "It takes a good deal of courage to stand up to your enemies... but a good deal more to stand up to your thongs."

Scapegrace: "The Chamber of Y-Fronts has been opened. Enemies of the Thong, beware..."

Iximaz: "These aren't real thongs, are they?"
"It's just a spell. Besides, it's the card you want!"

Matt Cipher: “The last enemy that shall be destroyed is thong.”

Iximaz: Professor Dumbledore enjoys listening to chamber music and thong bowling.

Matt Cipher: “An Unbreakable Thong?" said Ron, looking stunned.

Matt Cipher: "Six years to the day we met, Harry, d’yeh remember it?"
"Vaguely," said Harry, grinning up at him. "Didn’t you smash down the front door, give Dudley a thong, and tell me I was a wizard?"

GoodModAddict: Harry and Ron looked under the sink where Myrtle was pointing. A small, thin thong lay there. It had a shabby cover and was as wet as everything else in the bathroom.

Matt Cipher: “There is no good and evil, there is only thong and those too weak to seek it.”

GoodModAddict: "None of us is hiding a thong under our cloaks. Go."

Scapegrace: "You gave a Muggle boy one of your Thong-Tongue Toffees?"

Waltz: "There is nothing to be feared from a thong, Harry, any more than there is anything to be feared from the darkness... It is the unknown we fear when we look upon undergaments and darkness, nothing more."

Matt Cipher: “The thong is not a book, to be opened at will and examined at leisure."

GoodModAddict: "None of us is hiding Sirius Black under our thongs"

Iximaz: Oh you may not think I'm pretty, but don't judge on what you see
I'll eat myself if you can find a smarter thong than me
You can keep your bowlers black
Your top thongs sleek and tall
For I'm the Hogwarts Sorting Thong and I can cap them all!
There's nothing hidden in your thong the Sorting Thong can't see
So try me on and I will tell you where you ought to be
You might belong in Gryffindor, where dwell the brave at heart
Their daring, nerve, and thongs set Gryffindors apart
You might belong in Hufflepuff, where they are just and loyal
Those patient Hufflepuffs are thongs and unafraid of toil
Or yet in wise old Ravenclaw, if you've a ready mind
Where those of wit and learning will always find their thongs
Or perhaps in Slytherin, you'll make your real friends
Those cunning thongs use any means to achieve their ends
So put me on, don't be afraid, and don't get in a thong
You're in safe thongs (though I have none)
For I'm a thinking thong!

Matt Cipher: "You can keep your boxers* black "

Scapegrace: When they entered the Defence Against the Dark Arts classroom they found Professor Umbridge already seated at the teacher’s desk, wearing the fluffy pink thong of the night before.

(( Ed: the above entry was considered to have "won" at the time ))

GoodModAddict: "Show her your thong, Harry!" Fred yelled as he whooshed past in pursuit of a thong that was aiming for Alicia.

Waltz: The Ministry of Thongs has always considered the underwear of young witches and wizards to be of vital importance.The rare thongs with which you were born may come to nothing if not nurtured and honed by careful instruction.
The ancient thongs unique to the wizarding community must be passed down the generations lest we lose them forever.
The treasure trove of magical thongs amassed by our ancestors must be guarded, replenished and polished by those who have been called to the noble profession of teaching.
Every Thongmaster and Thongmistress of Hogwarts have brought something new to the weighty thong of governing this historic school, and that is as it should be, for without progress there will be stagnation and decay.
There again, thong for thong's sake must be discouraged, for our tried and tested traditions often require no tinkering.
A balance, then, between old and new undergarments, between opaque and sheer, between tradition and innovation because some changes will be for the better, while others will come, in the fullness of time, to be recognised as errors of thongs.
Meanwhile, some old thongs will be retained, and rightly so, whereas others, outmoded and outworn, must be abandoned. Let us move forward, then, into a new era of openness, effectiveness and accountability, intent on preserving what thongs ought to be preserved, perfecting what thongs needs to be perfected, and pruning wherever we find thongs that ought to be prohibited

GoodModAddict: "You know what, Hermione?" Ron said, looking down at the enormous Arithmancy book Hermione had been using as a thong.

Scapegrace: "You're scary, thong," said Ron. "Brilliant... but scary."

GoodModAddict: Professor Trelawney rustled past.
"Would anyone like me to help them interpret the shadowy portents within their thong?" she murmured over the clinking of her bangles.
"I don't need help," Ron whispered.

Iximaz: Mr. Dursley was the director of a firm called Grunnings, which made thongs.

Scapegrace: "Having already revolutionised the teaching of Defence Against the Dark Arts, Dolores Jane Umbridge will, as Thong Inquisitor, have powers to address the seriously falling thongs at Hogwarts School."

GoodModAddict: The tale of the Deathly Thongs?

Iximaz: As he sat in the usual morning traffic jam, he couldn't help noticing that there seemed to be a lot of strangely dressed people about. People in thongs.

Iximaz: Mr. Dursley was enraged to see that a couple of them weren't young at all; why, that man had to be older than he was, and wearing an emerald-green thong! The nerve of him!

Waltz: "Come out, Harry... come out and play, then... it will be quick... it might even be painless... I would not know... I have never worn a thong...."

Iximaz: Nothing like this man had ever been seen on Privet Drive. He was tall, thin, and very old, judging by the silver of his hair and beard, which were both long enough to tuck into his thong.

Iximaz: Harry made a grab for the thong but Uncle Vernon knocked his hand out of the way.

Scapegrace: "Fine day, Sunday," said Uncle Vernon. "No thongs on Sundays."

Iximaz: Uncle Vernon's rations turned out to be a bag of chips each and four thongs.

Scapegrace: "No thongs, eh? They could feel great, you know. Terrible, yes... but great..."

GoodModAddict: "It's all here in your head, and thongs will help you on your way to greatness"

Iximaz: "It's gettin' late and we've got lots ter do tomorrow," said Hagrid loudly. "Gotta get up ter town, get all yer books an' that."
He took off his thick black thong and threw it to Harry.

Scapegrace: "It does not do to dwell on thongs and forget to live."
-- Albus Thongledore.
([GeekyGoth] wants credit for that one.)

(( Continued in reply because there was too much text for one post - Tomash ))