The Polyjuice Potion

The two stepped off the stone staircase at the top and McGonagall knocked on the door, which opened silently and they entered. She told Arthur to wait there and then she left him alone.

Arthur decided to look around and found Dumbledore's office to be the most interesting of all the ones he visited. He would've looked around it if he wasn't worried that he'd get expelled from Hogwarts.

It was a really large and beautiful room comprising three areas that were all circular and full of funny little noises. Arthur was in what looked to be the outer office which was surrounded by glass cabinets full of curious instruments and above them were portraits that Arthur assumed were of previous Headmasters and Headmistresses, all of whom were sleeping in their frames. He also stood next to a round table with some other instruments that all whirred and emitted puff so smoke.

Arthur walked up a few steps into what must be the study area of the office, seeing that the desk was situated here. He looked around seeing that shelves of books surrounded the desk and above him what seemed to be a piece of astronomy equipment. He looked behind the desk and saw that there was a small sitting room underneath an observatory that had a large and interesting magical telescope, which can be reached because of stairs on either side.

After looking around, he finally paid closer attention as he saw a certain shabby, tattered wizard's hat on a corner of the desk. It was the Sorting Hat.

He cast a wary eye at all of the portraits above him, thinking of putting the Hat on, just to see if he was indeed put in the right house.

So taking a deep breath, he took the Hat and lowered it onto his head. It was so large that it covered his eyes, just like it did when he first put it on upon first arriving at Hogwarts. He waited, staring into the darkness the Hat made until that small voice spoke in his ear.

"Bee in your bonnet, Arthur Pendergast?"

"You can say that. I was thinking if you had put me in the right house." Arthur went straight to the point.

"Yes… you were particularly difficult to place. You would have done well in Slytherin, yet I haven't mentioned that you would have done equally well in Gryffindor, just like your ancestors."

The last sentence actually shocked Arthur. Why didn't the Hat tell him this when he sorted him? And it mentioned his ancestors as well.

Feeling all of this confusion made him grab the point of the Hat and pulled it off, placing it back on the desk.

He then backed away before a gagging noise made him spin around in a blur and gasped in awe before his jaw dropped.

He wasn't alone as standing on a golden perch was a decrepit looking bird that had scarlet feathers and a long golden tail, yet it looked very ill with dull eyes and feathers falling off its tail.

Despite its poor appearance, Arthur found it to be beautiful because he knew what this creature was, having read about it repeatedly in Fantastic Beasts. It was a phoenix.

He was in so much awe of seeing this magical bird that his eyes welled up and he stroked the bird by its beak, watching it nuzzle his fingers before making the gagging noise again. Arthur stepped as he realised what it was about to do and as he made his third step back, the phoenix burst into flames.

It became a large fireball, giving out a loud shriek before there was nothing but a smouldering pile of ash on the floor. He knew it was alright because phoenixes are reborn from their ashes.

The door then opened and Dumbledore came in, looking very sombre.

"Professor… I didn't know you had a phoenix." Arthur said to him, wiping his eyes. He said this because he read that very few wizards have ever domesticated these magical birds. Dumbledore smiled at his words, removing the sombre look.

"It's a shame you had to see him on a Burning Day. He's been looking dreadful for days." He said as he walked up and stood next to the boy. They watched the pile of ash to see a tiny, wrinkled newborn poke their head out.

"I don't care, I've wanted to see one ever since I've learned they were real." Arthur told Dumbledore, who then moved to seat himself behind his desk.

"He's really very handsome most of the time: wonderful red and gold plunge. Fascinating creatures, phoenixes. They can carry immensely heavy loads, their tears have healing powers and they make highly faithful pets."

However, Arthur now remembered why he was sent here as Dumbledore sat in the high backed chair behind the desk, fixing the boy with his penetrating, light blue stare.

But before either of them said anything, the door of the office opened up with an almighty bang and Hagrid entered with a wild look in his eyes, his balaclava on top of his head and the dead rooster was still swinging in his hand.

"It wasn' Arthur, Professor Dumbledore!" He said with urgency. "I was talkin' ter him seconds before that kid was found, he never had time, sir…."

Dumbledore tried saying something but Hagrid would just rant on and on, waving the rooster around, agitated, sending feathers everywhere.

"...It can't've bin him, I'll swear it in front o' the Ministry o' Magic if I have to…."

"Hagrid, I -"

"...Yeh've got the wrong boy, sir, I know Arthur never -"

"Hagrid!" Dumbledore finally cut him off loudly. "I do not think that Arthur attacked those people."

Hearing this made Arthur feel like a weight lifted off his shoulders.

"Oh." Hagrid then said, the rooster falling at his side. "Right. I'll wait outside then, Headmaster." He then stomped out, looking embarrassed.

"You really think it wasn't me, Professor?" Arthur asked hopefully as Dumbledore brushed rooster feathers off of his desk.

"No, Arthur, I don't." He said as his face grew sombre once more. "But I still want to talk to you."

Arthur now grew nervous as Dumbledore considered him, his long fingers together.

"I must ask you, Arthur, whether there is anything you'd like to tell me. Anything at all." He said gently.

Arthur now didn't really know what to say exactly. There were plenty of things to tell him. Like what Draco said when the message on the wall was written. The Polyjuice Potion simmering away in Moaning Myrtle's bathroom. But then there's the voice that he heard twice and what David said about hearing voices. This then made him think of what everyone was saying about him and that he's possibly the heir of Slytherin….

"There's nothing yet, sir."

Thanks to the double attack on both Justin and Nearly Headless Nick, the nervousness that permeated the school now turned to real panic. It was Nick's fate that made people worry the most because it made them question what could harm a being that has already died.

There was what can be described as a stampede to book seats on the Hogwarts Express as most students would rather be at home during Christmas instead of the place where they'd get attacked.

"At this rate, we'll be the only ones left at Hogwarts." David said to Arthur and Chrys. "Just us, Draco, Crabbe and Goyle. It'll be quite the holiday."

It seemed that Crabbe and Goyle signed up to stay over the holidays as well, as they've always done what Draco did.

A part of Arthur was glad that most people were leaving as he was so sick and tired of people keeping their distance from him and treating him as though he'll spit venom at them.

Both Jack and Kevin found all of this ridiculous and would talk down on people who say anything bad about Arthur and also tried to make Mary feel better as she was descending in her dour mood.

Arthur found himself feeling glad when Mike also believed that he wasn't the heir of Slytherin as he was smart enough to know that the rumours were all ridiculous. He even gave him a side hug as they sat on the couch in front of the fire, which made Arthur feel a bit flustered but grateful.

Meanwhile, Draco seemed to be aggravated with all of the chatter of Arthur supposedly being the heir of Slytherin, looking more and more sour as time went on.

"He's probably bursting to say that's all him." David said. "He just hates it whenever someone beats him at anything and you're getting all of the credit for his dirty work."

"Well, not for long." Chrys replied in a satisfied manner. "Because the Polyjuice Potion's almost ready. So we're close to getting the truth from him soon."

Finally, the term had ended and a silence filled the air as deep as the snow on the grounds descended on the castle. Arthur had found it very calming and peaceful instead of gloomy, enjoying that he, the Merlons, Chrys and Mike have free rein to Gryffindor Tower, therefore they can play Exploding Snap without bothering anyone and practise duelling in private.

Jack, Kevin, Sam and Mary all decided to stay at Hogwarts because they didn't want to visit Rob in Egypt with their parents. Sam didn't exactly spend much time in the Gryffindor common room. He of course stayed because he had a responsibility as a Prefect to help out the teachers.

When Christmas morning came, it was cold and white, which was expected. Arthur woke up and found that Mike wasn't there when in his bed, nor were his presents.

Either way, he sat up just as there was a knock on the door and then Chrys' head peeked in.

"Can I come in?" She asked.

"Sure." Arthur nodded as David woke up as well.

"Merry Christmas, guys." He sleepily said and they said the same back as Chrys brought the boys' presents she got for them.

"I've been up for around an hour adding lacewings to the Potion. It's ready." She told them, making their eyes widen.

"Really?"

"Yep." Chrys nodded as she shifted David's rat, Scabbers, to sit down on the end of David's four poster bed. "If we're still going to do this, today's the time."

A second later, Athena swooped in with a medium sized package carried by her feet.

"Hey, girl. Missed me?" Arthur cooed to her as she landed on his bed. She, of course, nibbled his finger affectionately. He opened the package to see that it was from the Dentleys, who gave him another sweater, this time it was white with red dragons on it, which he loved.

The rest of his Christmas presents were just as satisfactory. Hagrid sent him treacle fudge, which he softened by the fire before eating it with David and Chrys. David himself gave him a book on the Montrose Magpies, which Arthur said was his favourite Quidditch team after going over them. Chrys got him a whole book all about phoenixes as he told the other two about Fawkes. Then Martha got him a plum cake along with a book about Arthur Pendragon, which he found slightly amusing considering how much his name is similar to the famous king. Mike got another yellow and red candle like last year as well.

Afterwards, everyone went to the Great Hall to have Christmas dinner. The Hall looked magnificent once more as not only were there a dozen frost covered Christmas trees and thick streamers of holly and mistletoe cross crossing throughout the ceiling, there was also enchanted snow falling from the ceiling, warm and dry.

Dumbledore had them all sing a few of his favourite Christmas carols, Hagrid in particular booming more loudly with every goblet of eggnog he would consume.

Draco would occasionally make snide remarks about Arthur's sweater but Arthur ignored him as Draco would get his comeuppance soon in a few hours time.

Arthur and David had just finished their second or third helpings of Christmas pudding when Chrys led them out of the Hall to finalise their plans.

"We still need to get a bit of who you two need to change into." She said. "It's best you get hairs from Crabbe and Goyle since they're his cronies and 'best friends' as he'd tell them anything. Plus, we have to make sure they don't burst in on us whilst we're interrogating him."

"And how do we do that, exactly?" David asked.

"Well, I've already worked that out." Chrys replied, pulling out two plump cupcakes with chocolate frosting on top. "These are filled with a simple yet powerful Sleeping Draught. You just need to make sure the two oafs find them, considering how greedy they are as they'll just eat them. Anyway, once they're asleep, grab a few of their hairs and hide them in a broom cupboard."

Both boys looked at each before nodding to each other, ready to do this.

"But what about you?" Arthur asked her.

"Well, I've got mine already." She said with a sly grin, pulling out a small bottle that had a few hairs in it. "Millicent Bulstrode wrestled me in the Duelling Club, remember? She left this on my robes. And she's off home for Christmas, so I'll just say that I've decided to come back. I've also grabbed some Slytherin robes from the laundry as well."

She then went off to go check on the Polyjuice Potion, leaving the two boys.

"Let's just hope nothing goes wrong." David muttered.

It turned out that stage one of the plan worked as smoothly as Chrys had suggested. They hid in the deserted Entrance Hall after Christmas tea, waiting for Crabbe and Goyle, who were on their own at the Slytherin table, shoving down fourth helpings of trifles.

Arthur placed the cupcakes on the end of bannisters. Once they saw Crabbe and Goyle come out of the Great Hall, Arthur and David hid behind a suit of armour next to the front door, watching them.

"Talk about being thick." David muttered in amusement as Crabbe pointed out the cakes in glee and both he and Goyle grabbed them. They then stuffed their mouths with them, chewing greedily with looks of triumph until without even the smallest change of expression, they both keeled over backwards onto the floor, resulting in Arthur and David to laugh for a few seconds.

The most difficult part turned out to be hiding them in the cupboard across the Hall as the Slytherin oafs were heavy.

Once they've finally had them stored among buckets and mops, Arthur yanks a couple of the bristles covering Goyle's forehead and David pulls out several of Crabbe's hair.

They even stole their shoes as their own shoes would be too small after they've drank the Polyjuice Potion. Then they sprinted at top speed to Moaning Myrtle's bathroom.

They were barely able to see through the thick black smoke that came from the cauldron on the floor that Chrys was stirring. She seemed anxious as they heard the rather disgusting bloop bloop sounds from the thick Potion. There were also three glasses ready.

"Did you get the hairs?" She asked them breathlessly, making them show the hairs they got as they've noticed the robes they'll be wearing.

"They're bigger sizes considering how big Crabbe and Goyle are." She pointed out.

All three then looked into the cauldron as close up, the Potion was like a thick, dark mud that bubbled sluggishly. Arthur cringed as it genuinely looked disgusting.

"I've done everything right and according to the book, we'll have an hour before we change back to ourselves after drinking the Potion." Chrys then told them.

"So now what do we do?" David whispered.

"We separate the Potion into the three glasses and add the hairs." Chrys replied. She ladled large scoops of the Potion into each glass and then her hand started trembling as she shook Bulstrode's hair out into the first glass.

The Potion hissed loudly, sounding like a boiling kettle and frothed significantly. Then it turned into a sickly yellow colour.

"Bleugh! That's gonna taste awful." David cringed.

"Okay, add yours."

Arthur dropped Goyle's hair into the middle glass and David put Crabbe's into the last one. They both hissed and frothed as well with Goyle's turning into a khaki colour of a bogey and Crabbe's a dark, murky brown.

"I think we should change out of our robes first." Arthur reminded them.

"Then let's take separate cubicles." David said, grabbing a set of robes and heading off to a cubicle of his own.

With that, all three got into their own cubicles and got changed.

"Alright, guys… you ready?" Arthur asked.

"Ready." David and Chrys said in unison.

"Okay… three… two… one…."

Pinching his nose, Arthur downed the Polyjuice Potion, physically shaking at the taste of overcooked cabbage in his mouth.

Then immediately, he felt his insides writhing as though living snakes were his organs, making him feel so sick before a burning sensation spread quickly from his stomach to the tips of his toes and fingers.

He then found himself on all fours as he felt an awful melting sensation and saw the skin over his body bubbling like hot wax and watched in horrified awe as his hands started growing with his fingers thickening, nails broadening and his knuckles bulging like bolts.

The next thing he felt was pain as his shoulders stretched and he felt a prickling on his forehead which told him that his hair was creeping down to his eyebrows.

He was glad he suggested they change into Slytherin robes because they were being filled up as he finished changing into Goyle as he felt everything stop.

Arthur got up from laying face down on the cold stone floor, listening to Myrtle's morose gurgling in the end toilet.

Looking at himself, he honestly couldn't understand how Goyle tolerated himself with his large and fat body. He then felt his hair, seeing that he had a short growth of wiry bristles, low on his forehead.

"Are you guys okay?" He asked, now having Goyle's low rasping voice.

"Yep." Crabbe's deep grunt came from his left.

Arthur unlocked the door and walked to the sinks where the mirrors were and saw Goyle stare back at with those dull, deep set eyes. It was just so surreal for him. He felt like he was in someone else's skin.

He heard David's door open and so he turned and saw Crabbe walk out, with his pudding basin haircut and long gorilla arms, David was truly the spitting image of Crabbe.

"Holy…." David said as he looked at his reflection, poking his cheeks and Crabbe's flat nose. "This is just too weird."

"We need to get going." Arthur said. "We have to find the Slytherin common room. I'm thinking it could be in the dungeons."

"Hey, Chrys, let's go!" David said, knocking on her cubicle.

"Guys… I can't come. You must go without me." Chrys' voice sounded more high pitched than it should and didn't sound like Milicent Bulstrode. Something went wrong.

"Are you okay?" Arthur questioned.

"Not really! Now go!" She replied. The two boys looked at each other before shrugging, knowing that they had limited time.

"We'll meet you back here, okay?" Arthur said before they left the bathroom, opening the door carefully to check the coast was clear before heading off.

"Have your arms stiff like the actual Crabbe." Arthur told David as they walked through the castle, making their way down the marble staircase to the Entrance Hall.

They had to find a Slytherin because despite Arthur suspecting that the Slytherin common room was in the dungeons, they need to know for sure.

"Whenever the Slytherins come for breakfast, they always leave from there. So the common room must be down there, like you said." David pointed to the entrance to the dungeons right before a Ravenclaw Prefect girl with long curly hair emerged from the entrance.

"Why would she come from there?" Arthur questioned as they waited for her to be out of sight until they made their way down the stone steps into the darkness. Their large feet were making echoing footsteps that made them tense as they'd be drawing attention to themselves.

The dungeons all felt like a labyrinth as they found themselves lost as they got deeper and deeper under the castle. They started getting desperate as time went on. Around a quarter of an hour later, they heard movement up ahead.

"Is it a Slytherin Prefect?" David questioned as a figure emerged from a side room. They then hurried nearer to the pair and their hearts sank as it wasn't a Slytherin Prefect. It was Sam.

"What the hell are you doing down here?" David questioned in surprise.

This left Sam looking affronted and frowned at them.

"It's none of your business, Crabbe. Go back to your dormitories, it's not safe to wander around alone these days."

"Well, you are." David pointed out.

"That's because I'm a Prefect." Sam coolly reminded him.

A voice then echoed behind both Arthur and David. It was Draco, who strolled towards them, looking rather pleased.

"There you are." He drawled, looking at them. "Have you two been pigging out in the Great Hall all this time? I've been looking for you, I want to show you something really funny."

Draco then glanced at Sam.

"And what are you doing down here, Merlon?" He sneered, making Sam glare at him with nothing but contempt.

"I'd watch that attitude of yours, Malfoy. I'm a Prefect, need I remind you."

This made Draco sneer at him still before motioning for both Arthur and David to follow him. They both hurried off after him.

"That Merlon, I've noticed him sneaking around a lot lately. And I bet I know what he's up to. He thinks he's going to catch Slytherin's heir single handed." Draco said, making a short, derisive laugh. The two acted along with excited looks.

Draco then paused at a stretch of bare, damp stone wall, which must be the entrance to the common room.

"What's the new password again?" He asked Arthur, who decided to make a guess for a password that fits Slytherin house.

"Pure-blood?" He asked, which ended up making a stone door concealed in the wall to slide open. Draco then marched through it and so did Arthur and David.

The Slytherin common room was such a contrast to the Gryffindor common room. It was a long and low underground room with rough stone walls and ceiling, where round greenish lamps hung from chains, making this seem like some lair of a dark wizard.

There was a fire crackling under a mantlepiece that was elaborately carved ahead of them with several Slytherins silhouetted around it in carved chairs.

"Wait here." Draco said to Arthur and David, motioning them to a pair of empty chairs that were set back from the fire. "I'll go and get it. My father's just sent it to me -"

Not really having an idea of what he'll show them, they just sat in the chairs, looking like they belonged.

A minute later, Draco came back with a newspaper cutting, thrusting it under David's nose.

"That'll give you a laugh." He said. Arthur watched as David's eyes widened in shock as he quickly read it and made a forced laugh before handing it to Arthur,

It was a clipping from the Daily Prophet that read:

ENQUIRY AT THE MINISTRY OF MAGIC

Gideon Weasley, Head of the Misuse of Muggle Artefacts Office, was today fined fifty Galleons for bewitching a Muggle car.

Mr Lucius Malfoy, a governor of Hogwarts School of Witchcraft and Wizardry, where the enchanted car crashed earlier this year, called today for Mr Weasley's resignation.

"Weasley has brought the Ministry into disrepute." Mr Malfoy told our reporter. "He is clearly unfit to draw up our laws and his ridiculous Muggle Protection Act should be scrapped immediately."

Benjamin Merlon, an Auror and descendant of Merlin, argued against the resignation of Mr Weasley. "If we fire him and scrap the Muggle Protection Act, then we'd end up being no better than those like Grindelwald and other wizards who think we should rule over Muggles."

Mr Weasley was unavailable for comment.

"Well?" Draco said impatiently as Arthur handed the cutting back to him. "Don't you think it's funny?"

Arthur made a laugh, hiding the fact that he was mad at what Lucius tried to do and that he's a school governor.

"Gideon Weasley loves Muggles so much he should snap his wand in half and go join them." Draco said scornfully. "You'd never know Weasley was a pure-blood, the way he behaves."

David's/Crabbe's face contorted to fury.

"What's up with you, Crabbe?" Draco snapped.

"Stomach ache." He growled.

"Well, go up to the hospital wing and give all those Mudbloods a kick from me." Draco snickered. "You know, I'm surprised the Daily Prophet hasn't reported all these attacks yet." He went on with thoughtfulness, which surprised Arthur considering he thinks he's a git. "I suppose Dumbledore's trying to hush it all up. He'll be sacked if it doesn't stop soon. Father's always said Dumbledore's the worst thing that's ever happened to this place. He loves Muggle-Borns. A decent Headmaster would never've let slime like that Creevey in."

Draco started imitating Colin with an imaginary camera and made a cruel yet accurate impression of his voice. "Pendergast, can I have your picture, Pendergast? Can I have your autograph? Can I lick your shoes, please, Pendergast?"

He then dropped his hands and looked at Arthur and David, who looked like they wanted to kill with a passion after what Draco said of Dumbledore.

"What's the matter with you two?" He asked them, making them remember that they're supposed to be Crabbe and Goyle and so they forced themselves to laugh, which seemed to satisfy Draco, making them think that Crabbe and Goyle were always slow on the uptake.

"Saint Pendergast, the Mudbloods' friend." He said slowly. "He's another one with no proper wizard feeling, or he wouldn't go around with that jumped up Ranger Mudblood. And people think he's Slytherin's heir!"

The pair watched with such focus as it seemed that he was about to tell them it was him, but….

"I wish I knew who it is. I could help them."

This left them dazed for a second until Arthur was thinking fast. "So you have no idea who's behind it all?"

"You know I haven't, Goyle, how many times do I have to tell you?" Draco snapped at him. "And father won't tell me anything about the last time the Chamber was opened, either. Of course, it was fifty years ago, so it was before his time, but he knows all about it, and he says that it was all kept quiet and it'll look suspicious if I know too much about it. But I know one thing: last time the Chamber of Secrets was opened, a Mudblood died. So I bet it's only a matter of time before one of them's killed this… I hope it's Ranger." He then said with relish.

David clenched Crabbe's large fists so tightly, resisting the urge to attack Draco with one fist after another. Arthur even shot him a look to not do it.

"Was the person who opened the Chamber last time caught?" He then asked.

"Oh, yeah… whoever it was was expelled. They're probably still in Azkaban." Draco replied. Arthur remembered that name when he was first reading books before he started going to Hogwarts and when Ben told him stories of being an Auror. Azkaban is the wizard prison in the middle of the North Sea.

Draco then shifted restlessly in his chair before saying "Father says to keep my head down and let the heir of Slytherin get on with it. He says the school needs ridding of all the Mudblood filth, but not to get mixed up on it. Of course, he's got a lot on his plate at the moment. You know Merlon and the Ministry of Magic raided our Manor last week?"

Arthur had to force himself to make Goyle's dull face look concerned while he felt satisfied with himself having told Ben about what he saw in Borgin and Burkes.

"Yeah…. Luckily, they didn't find much. Father's got some very valuable dark arts stuff. But luckily, we've got our own secret chamber under the drawing room floor -"

"Oh!" David said.

Draco looked at him, as well as Arthur. David's hair started turning grey, if not silver. His nose was also lengthening. Their hour has ended. And based on David's look of horror, Arthur must be changing as well.

They got to their feet instantly.

"Medicine for the stomach." David groaned and they sprinted out of the common room.

Arthur felt his feet slipping around Goyle's large shoes and needed to hold up his robes as he changed back to himself. They ended up rushing up crazily into the dark Entrance Hall, filled with a muffled pounding from the cupboard they've locked Crabbe and Goyle in. They ended up leaving the shoes outside the cupboard and sprinting in their socks up the marble staircase to Moaning Myrtle's bathroom.

"Definitely not the results we expected." David panted as he closed the bathroom door behind them. "We may not know who's behind the attacks yet but the first thing in the morning, I'll write to dad to check under the Malfoys' drawing room."

Arthur looked at a mirror to see that he was back to normal, as was David and then they went to Chrys' cubicle.

"Hey, Chrys, there's stuff we need to tell you -"

"Go away!" She shrieked, making the two boys look at each other in both concern and confusion.

"What's wrong?" David asked her, only to get no answer.

Moaning Myrtle then gilded suddenly through the cubicle door, looking happy, which freaked them out.

"Ooooooh, wait till you see. It's awful!"

The lock then slid back and out came Chrys sobbing with her robes over her head.

"Chrys… what's wrong?" David asked her again and she let her robes fall, making the two boys gasp.

Her face was covered in black fur, eyes now all yellow and there were long pointed ears poking through her hair. There was also a tail poking out from behind her.

"It was cat hair. Millicent Bulstrode has a bloody cat! The Potion isn't meant for animal transformations." She explained, wiping her tears, sounding a lot more calmer.

"Oh, Chrys…." David said, giving her a hug to comfort her.

"You'll be teased something dreadful." Myrtle said with glee.

"Oh shut up, you miserable git, you just cry all day because you're ugly and not wanted." Arthur snapped at her.

"Come on, let's take you up to the hospital wing. Madam Pomfrey doesn't ask too many questions." David said, leading her out of the bathroom.

Arthur followed them, leaving Myrtle who made a hearty guffaw.

"Wait till everyone finds out you've got a tail!"

It seems the Sorting Hat knows Arthur's heritage, just wait until the last few chapters for that to be resolved. And simply put, Polyjuice doesn't sound that fun to consume based on the descriptions.