If you think about it you've involuntarily answered your own question if somewhat in the abstract. You're doing this for Halloween, ergo it's a costume, one perhaps more drastic in acquisition, but a costume none-the-less. You'll get ribbed, then because it's only supposed to be a transitory thing, be pretty much forgotten as it grows back. Yes, you'll get comments and questions about your ever lengthening locks but then it will pass a certain visual point and it will be forgotten.
IF that's what your actual intent is. To shave your head as a prank. Or, perhaps, are you really asking us, "What happens if I shave it all off as that's what I want?"
