"What do you need boy robes for?" inquires Madam Malkins.
"I'm sometimes a boy," the girl explains.
"What?"
"Look—"
"… You could try doing the floating better? Or – I haven't actually read the books, I don't know what things there are apart from, uh, colour change or something?"
She looks at her bag, which is currently a plain brown.
"… Don't make it too bright and sure, go ahead."
He touches the bag, frowns a bit, and says, "Colovaria!"
...and it is now bright orange with red specks.
"It's really not my style," says Thea, biting her lip a little. "Do you know if it's permanent?"
"Like, a group of pupils from each house? From the upper years? Who look after first years and stuff?"