Mary Potter and The Philosopher's Stone (Harry Potter's Transgender Twin Sister)

The Keeper of Keys

That night it was stormy, the Potters and Dursleys stayed at a tall house, on a rock island somewhere out at sea. The family slept, with Mary and Harry on the cold, dirt floor and Dudley sleeping on a sofa. Harry had drawn a birthday cake which read, Happy Birthday Harry and Mary. Harry looked at Dudley's watch, which beeped 12:00.
"Make a wish, Mary." Said Harry to his twin. They blew out the "candles" on the drawn birthday cake.
Suddenly, the door thumped, in sync with the thunder flashing. Harry jumped. The door thumped again and Dudley, Harry and Mary jumped up and backed away. Harry hid behind a wall, and Dudley cowered on a windowsill whilst Mary stood behind the sofa. Petunia and Vernon appeared, with Vernon holding a double barrel gun.
"Who's there? Ahh!" Cried Vernon.
The door banged again and then fell down, and a giant man appeared. As he came into the clear lighting, he was revealed to be Hagrid, who, unbeknownst to them, helped drop the twins at privet drive by flying them there on a motorcycle.
"Sorry 'about that." Said Hagrid and he put the door back up.
Vernon aimed his gun at Hagrid.
"I demand that you leave at once, sir! You are breaking and entering!" Vermin ordered.
As Petunia quietly gasped in fear, Hagrid grabbed the gun and bent it upwards.
"Dry up, Dursley, you great prune." said Hagrid intimidatingly.
The gun fired upwards, blasting a hole in the ceiling, causing the two to shriek in fear.
Hagrid noticed Dudley. 
"Boy, I haven't seen you since you was a baby, Harry, but you're a bit more along than I would have expected. Particularly 'round the middle!" Said Hagrid
"I-I-I'm not Harry." Whimpered Dudley
Harry revealed himself
"I-I am" said Harry
"Yeah, and I'm Mary" said the girl,  jumping over the sofa.
"well, of course you are! Got something for ya. 'Afraid I might have sat on it at some point! I imagine that it'll taste fine just the same. Ahh. Baked it myself, Words and all. Heh." Said Hagrid,
he handed a white box to Harry
Harry opened the box,  and inside was a cake which read "Happee Birdae Harry and Mary" in green icing.
"Thank you!" Said Mary.
"It's not every day that your young man and lady turn eleven, now is it aye?" Said Hagrid.
Hagrid sat down on the sofa, took out an umbrella and pointed it at the empty fire. Two sparks flew out and the fire started. The family gasped.
Harry put the cake down and said "Excuse me, who are you?".
"Rubeus Hagrid. Keeper of keys and grounds at Hogwarts. Course, you'll know all about Hogwarts".
Mary and Harry shared a look ,  "sorry, no" they both said.
"No? Blimey, didn't you ever wonder where your mum and dad learned it all?" Asked Hagrid.
"Learned what?" Asked Harry, frowning at Mary who was turning cartwheels on the floor.
"You're a wizard, Harry, and Mary's a Witch.
Harry looked confused and Mary stopped mid cartwheel, falling on her bum.
"We're what?" Asked the twins, Mary still on the floor.
"A wizard and Witch. And thumping good ones at that, I'd wager. Once you train up a little." Said Hagrid.
"No, you've made a mistake. I can't be...a-a wizard. I mean, I'm just... Harry. Just Harry." Said the male twin.
"Well I'm just glad to be called a Witch, not a Wizard" said Mary greatfully, but no one was listening.
"Well, just Harry. Did you ever make anything happen? Anything you couldn't explain when you were angry or scared?" Asked Hagrid knowingly.
"SNAKE" shouted Mary to Harry, who still looked doubtful.
Hagrid handed Harry and Mary the same letters that has been sent the past while. Harry opened his, first and began to read aloud,
"Dear, Mr. Potter. We are pleased to inform you that you have been accepted at Hogwarts' School of Witchcraft and Wizardry.".
"They'll not be going! We swore when we took them in, we’d put a stop to this rubbish!" Said Vernon to Hagrid.
"You knew? You knew all along and you never told us?" Exclaimed Harry.
Mary did the slit throat to her aunt.
"Of course we knew. How could you not be? My perfect sister being who she was. Oh, my mother and father were so proud the day she got her letter. We have a witch in the family. Isn't it wonderful? I was the only one to see her for what she was. A freak! And then she met that Potter, and then she had you, and I knew you'd be just the same, just as strange, just as ... abnormal. And then, if you please, she went and got herself blown up. And we got landed with you." said Aunt Petunia in a disgusted voice.
"Blown up? You told us our parents died in a car crash" shouted Mary, finally paying attention.
"A car crash? A car crash kill Lily and James Potter?" shouted Hagrid.
"We had to tell them something." said Aunt Petunia.
"It's an outrage! It's a scandal!" Cried Hagrid.
As the Dursleys argued with Hagrid, no one noticed Dudley taking the cake away.
"They'll not be going!" Shouted Uncle Vernon.
"Oh, and I suppose a great Muggle like yourself's going to stop them, are you?" Mocked Hagrid.
"Muggle?" Asked Harry.
Mary was busy trying to kill Aunt Petunia with a glare.
"Non magic folk." Hagrid explained. 
He immediately drew his attention back to Vernon in anger.
"These two have had their names down ever since they were born!" Hagrid Shouted.
As Hagrid was talking, Dudley was munching on the cake.
"They're going to the finest school of witchcraft and wizardry in the world, and they'll be under the finest headmaster that Hogwarts has ever seen, Albus Dumbledore".
Harry smiled upon hearing Dumbledore's name, Mary was still shooting daggers at Petunia.
"I will not pay for some crackpot old fool to teach them magic tricks!" Shouted Vernon.
Hagrid whipped out his umbrella and pointed it at Vernon, threateningly.
"Never, insult Albus Dumbledore, in front of me." Hagrid said in a low growling voice. Mary turned to look at her Uncle, and if looks could kill, there was no hope for Vernon.
Hagrid finally saw Dudley eating the twins' cake, and aimed his umbrella at the pig of a boy's rear. He fired a magic spark at it, causing a grey tail to grow.
"Ahh!" Screamed Dudley.
The Dursleys shrieked in both fright and horror, as they ran off out of sight. Harry laughed at this, so did Hagrid and Mary yelled "get wrecked pig arse".
"Oh, um, I'd appreciate if you didn't tell anyone at Hogwarts about that. Strictly speaking, I'm not allowed to do magic." Said Hagrid.
"Okay." Said Harry and Mary together.
"Ooh, we're a bit behind schedule. Best be off. He went off to the door and pulled it down again, before stepping out.
"Unless you'd rather stay, of course. Hmm?".
He walked out. Harry grinned, looked back at the direction where the Dursleys are gone, and grinned again, before grabbing his jacket and joined Hagrid on their journey to London, Mary had already skipped out infront and was singing.