Continuity mistake: At the end of the first Halloween, Loomis fires six audible shots from his gun (whether or not they all hit Michael is irrelevant). However, at the beginning of Halloween II, Loomis' gun can be heard firing off seven shots. Also the front view of the house from the first movie and second movie are two different houses. When Michael is shot he falls off the balcony which is on the side or rear. The second movie shows him falling off the front of the house. Different railings too.
Revealing mistake: In the beginning of Halloween 2, the scene where Dr. Loomis shoots Michael Myers repeatedly until he falls off the balcony is reenacted to reflect the events of the original Halloween. If you look carefully, you can see that the stuntman portraying Michael is actually walking backwards on a table until he haplessly falls off the balcony.
Trivia: Director Rick Rosenthal wanted to maintain the tactful and tasteful, slow-burn nature of the original film, and his original director's cut lacked blatant gore and nudity. However, writer/producer John Carpenter felt horror fans would not accept a film without extreme content due to the rise of various extremely graphic slasher-films in the wake of the original film. Thus, Carpenter went back and ghost-directed several new scenes to add in extra nudity and violence into the movie. (And if you watch the movie very closely, these reshoots can be pretty obvious, as they don't quite fit in with the rest of the film).
Sam Loomis: I ought to handcuff you to the wheel, but I have a feeling I'm gonna need you in there. Can I trust you?
Marshal: What have I got to lose, except my job?