Someone pls write this (HP Edition)
So, when someone takes polyjuice potion, they turn into the person the hair comes from, right? We can also assume that age transfers over; you can't take an adult's hair and expect to transform into the child version of them. So, theoretically, one could hold onto hair from someone when they're, say, 15, and turn into the 15-year-old version of them years later.
From this thought came this idea (set during PoA):
Harry is moping around his dorm while Ron and Hermione are at Hogsmeade. He's throwing a little tantrum at not being able to go when he accidentally finds a secret compartment under his bed.
Inside are 4 vials of hair, 2 black, one brown, and one sandy blonde, labeled J.P, S.B, R.L, and P.P, respectively.
Harry thinks nothing of it, finds it a little weird, but shrugs it off.
Later, he and Ron are commiserating about Harry's lack of Hogsmeade privileges when Ron has a brilliant idea: polyjuice potion!
They rush down to the common room and beg Hermione to help.
She argues that he'd be in danger, what with Sirius Black lurking about, and him staying in the castle is really for his own good. Besides, who would he polyjuice into that wouldn't already be there? She is not knocking someone out again.
Well, I'll just use this hair I found, Harry retorts (oh so logically and rationally 🙄). Also, how would Sirius Black even know it's me?
Hermione finally gives in.
After a month of brewing, the polyjuice is finally done. Harry randomly selects a vial from the compartment, basically skipping down to Moaning Myrtle's bathroom.
He drops the hair in, and it turns a dark, purple-black shade, like a really dark wine.
He tips it back and suffers through the transformation.
Thirty minutes later, Minerva McGonagall spots someone in The Three Broomsticks and passes out in a dead faint.
People rush about, trying to figure out what's going on, while a young, long-haired figure sneaks out with two other students before anyone can look too closely.
In the alley behind The Three Broomsticks, the three students sigh in relief, only to freeze as they come face-to-face with a massive black dog.
The dogs tilts it's head, whining in confusion as it stares into the face of...a 15-year-old Sirius Black?