What most people say is a mistake, is that in the scene where Jamie Lee Curtis is stabbing Michael Myers repeatedly with the knife in the hall way. You see her jab the knife in his chest and he falls down to the next floor. You still see the knife in his hand and he has one in his chest, but when it cuts back to Jamie, you see her drop the knife from her hand. (What people don't see is that she actually has two knives.)