"What do you need boy robes for?" inquires Madam Malkins.
"I'm sometimes a boy," the girl explains.
"What?"
"Look—"
"Probably?" he shrugs. "It's not guaranteed, I might be Ravenclaw? I'm probably not really cunning, though, or – uh, Gryffindorish?"
"Well I'll be a Ravenclaw, I'm sure! ...maybe Hufflepuff. But probably Ravenclaw!"
"I don't really know which is right, Professor Flitwick didn't want to tell me much about the Houses."
"Gryffindors are brave and loyal, Ravenclaws are book-smart and curious, Hufflepuffs are hard-working and form tight groups, Slytherins are ambitious and cunning?"
And then a young girl is at the door to the compartment, looking a bit nervous but holding her head high.
"Uh. H-hi."
In she comes! She has some luggage with her which she puts under the chair and then she looks around a bit and after a moment she sits.
"I think I'm gonna be a Slytherin, she thinks she's gonna be a Ravenclaw, he thinks he's gonna be a Hufflepuff, we need a Gryffindor to complete the set."