10. The Setting Doesn't Make Sense
Halloween is of course at the end of October, when the world is just touching on Winter. The film, however, was shot in the spring of 1978, with an incredibly short 20 day shooting schedule. Because of this, the set they worked on caused issues from the beginning.
The autumnal setting needed for the film had to be created artificially (more on that later!). But it also led to a fairly large discrepancy in the film.
In many scenes, the ground is strewn with browned leaves hand painted by production designer Tommy Lee-Wallace, yet the trees and bushes surrounding them are green, in more or less full bloom. There are, for the eagle-eyed, palm trees that appear as well, as the shoot occurred in California, not Illinois.
Carpenter wanted to do something to fix this issue, but the budget wouldn't allow it, so Halloween is a film that seems to be timeless in its setting - at least in so far as the greenery is involved.