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.
Other mistake: Watch the scene where the drunk Ben Tramer (wearing a similar Michael Myers mask) was hit by the speeding cop car and then pinned against the parked van before burning. Even taking out the equation of accidentally hitting Ben Tramer, what was the cop car doing speeding at that rate of speed, head on towards a parked van on a side street? Remember, we only hear screeching brakes AFTER the car hits Tramer, and we never see the cop car swerve or any of that to miss hitting the van. Seems that even if Tramer hadn't been there, the cop car was sure to barge head on right into that van.
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.
Continuity mistake: When Michael enters the Elrods' home and steals the knife, as he picks up the knife from where Mrs. Elrod had left it, there are several drops of blood that fall onto the lunchmeat, presumably from Michael's injuries from having been shot. A few seconds later when Mrs. Elrod walks back over to the lunchmeat and reaches for the knife and sees the blood, the droplet patterns are different.
Visible crew/equipment: On the Goodtimes DVD release of Halloween 2, just after Dr. Loomis blows up the hospital room the camera switches to the hallway where Laurie is running away. The explosion comes through the hallway and you can see the right side of the hallway shaking - this shows that the wall is a studio set wall. You can also see wires behind it and the wooden supports that are holding it up. (01:25:30)bkillah
Revealing mistake: In the scene where Marion is calling for help on the police car's 2-way radio, she speaks, "Marion Chambers with Doctor Loomis at the clinic; He's here." Right after that, the policeman on the other end of the radio starts to talk. However, Marion never lets go of the "talk" button on the radio's microphone, until the middle of the policeman's response to her request. You can't listen and receive anything on the radio while the button on the mic is pressed.
Continuity mistake: During the scene where Jimmy the paramedic finds Ms. Alves in the major surgery room on a stretcher with the blood completely drained from her body, while turning to walk out, he slips and falls back first in the pool of blood. Later, he finds his way to his car where Laurie had been hiding and attempts to get help. If you look closely, he still has the same shirt on, but it has no blood on it.
Continuity mistake: When the guy in the Myers mask is being chased by the Sheriff and Dr. Loomis, the guy is hit by a cop car which crashes into a van and causes an explosion. In an overhead shot you see the body fall on the hood of the car, but when Dr. Loomis gets a closer look, the body is pinned straight up against the car and burning.
Continuity mistake: At the very end of the first Halloween, Loomis' first shot hits Michael while he is struggling with Laurie. A few seconds later, he is staring down Loomis and breathing very heavily. At the beginning of Halloween II, the scene is reenacted to reflect the ending of the first movie, but here you cannot hear Michael breathing at all after being struck by Loomis' first shot.
Continuity mistake: Notice how Michael is taking/reacting to being hit by the bullets at the conclusion of the first Halloween - you see him writhe in pain, his hand shake and grab near his side, and his body contort and literally twist before falling off the balcony - a believable shooting death scene. When the scene was re-enacted at the beginning of part II, all Michael does is lazily walk backwards and fall off.