Based on Tumblr post by captainevilpants: Mary Poppins was a witch at Hogwart

….

Albus groaned as he felt sharp pokes to his side. "Leave me alone." He muttered, "Not morning yet."

Another vicious poke, "Albus. Up please."

Mary.

What in Merlin's name?

Rolling over, Albus was about to yelp at the sight of his best friend, only stopping when she cast a wandless Silencio on him, her usual calm expression on her face. When she was sure that he wasn't going to cry out and alert the other boys in the dorm, she removed the spell.

"What are you doing?" he hissed, words broken off by a long yawn, "You can't be in here!"

Mary just raised an eyebrow at him, "I was fancying something a little sweet. Care to join me?"

Albus rolled over, fully intending to bury himself deeper into the blankets and fall asleep.

"Albus…" she poked him again, "…. We're going to the kitchen."

"We? We have to set a good example, not sneak out in the middle of the night!"

But Mary hadn't appeared to have heard him, summoning Albus's clothes out of the drawer and flinging them at him. She had a one-track mind, and Albus knew there was no point in arguing with her.

Unwillingly, he rolled out of bed.

"Chop, chop!" She strode out of the room, "Let's go!"

…..

"You know how you want to teach someday?" Albus asked, as they snuck through the corridors, "You'll need to stop this, and actually set a good example."

Mary ignored him, easily finding the entrance to the kitchen and going inside.

"And why did I have to come with you anyway?"

"I just thought, with all the new responsibilities and our exams, this was the last bit of time we would be able to spend together… outside of prefect duties of course."

Albus frowned, "We- we can still be friends. There are plenty of things for us to do before we graduate. And afterwards, we can both work here!"

Raising an eyebrow, Mary smirked, "Are you sure you really want to work with me?"

"I can think of nothing more perfect."

….

Several decades later, one year away from retiring and focusing fully on the prospect of becoming a full-time nanny, Mary knocked on a very ordinary door, in the middle of a very ordinary neighbourhood.

When the door opened up, she smiled at the red-head standing there, a young boy standing behind her nervously.

"Lily Evans?"

….

"So, your name is Mary Poppins?!" Lily beamed, practically bouncing up and down in excitement, "Like the nanny from the film?"

"Ah, yes." Mary smiled fondly, "Walt. He was expelled from Ilvermorny, the American wizarding school, for charming cameras and making the photographs move. A bit of an odd duck, but he was nothing compared to Wonka. He has his own film you know."

"Willy Wonka is a wizard?"

"Oh yes." Mary nodded, "Slytherin. He's outwitted some of our top politicians for years and enjoys every moment of it." She seemed deep in thought for a few moments, before shaking her head and beaming, "Now, about your school supplies."