Post by mag3It's not you. His crest was, apparently, the "generic" Hogwarts Crest as
also worn by Moaning Mertile, Mdm. Hooch, and others. I wonder about
that - Is it cannon that you only wear your house's crest while you're
actually *in* the house, and the generic crest at all other times?
But then that would not explain Tom Riddle's wearing it even though he wears
Slytherin's colors. The explanation I thought of is that there was a time
when Hogwarts only had the students colors show in say, the tie and maybe
the sweater and not the rest of the uniform, and at some point it changed to
where students also wore badges as well, perhaps in an effort to make their
House affilliation more obvious at a distance.
In the books (canon), there is nothing about any House markings on the
clothing. There are no uniforms other than the plain black robes, black
hat, and black cloak with silver fastenings (not plain black frogs as in
the movies). They wear their own clothes under the robes, if they choose
to. When Harry and Co. change in CoS, all they need to do is get bigger
robes, not Slytherin robes, to pass as Slytherins. They don't have to
change neckties or anything. All the markings are from the movie.
I read somewhere about how it must have been odd to have to buy a robe with
the Hogwarts crest on it, THEN have to go through and get the additional
uniform stuff for your House as well, especially if you didn't have a lot of
money and no guess where you would be sorted. My only answer that I could
think of is that students are expected to buy a basic robe that has the
Hogwarts crest on it, then when they are sorted, that the items with their
house colors are given to them. Afterall, Hogwarts had to have some form of
budget for these sorts of things (or House elves to make them).
In the movie, when they arrive in their new dormitory, their House scarves
are waiting on the chairs. Presumably the rest of the House specific
uniform is there, too.
At that point, they could very possibly change their badges themselves, or
perhaps someone else helps them with it, i.e. their Prefects.
Yet another, sheerly magical possibility is that the crest on the newer
robes changes to your house. :)
I think it's done by House elves. If you look at them in Diagon Alley in
the second movie, you can see what the students wear when they are away
from the school but in wizard territory. If I recall correctly, most of
them wear the generic school uniforms they wore before they were sorted,
but Draco wears the Slytherin gear. (As does his father - his robe?
cloak? fastens with silver snakes.)
=Tamar