Continuity mistake: At the end of part one, Laurie's stab wound was just a streak of blood and none on her shirt at all. When they bring her out to the ambulance, there's now a lot of blood on her shirt and streaks of blood on her arm. (00:13:20)
Continuity mistake: When Michael is stalking the hospital corridors there is a scene when he hides in the baby unit and is observing the Head Nurse berate Nurse Karen for being late again. The scene switches back and forth between a close up of the two nurses talking to a shot from Michael's perspective of them from inside the baby unit. In the close up the Head Nurse's body is facing Karen, from Michael's perspective her body is facing towards him on the other side of the nurse station. (00:30:20)
Continuity mistake: After Laurie wanders into a hospital room and unsuccessfully tries to use the telephone there are a series of shots cutting back and forth between the room and Laurie looking out into the hallway. In the shots from inside the room the telephone shifts position at one point. (00:59:01)
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)
Revealing mistake: When Loomis shoots the marshal's window out, when he makes a u-turn you can see the tire marks on the road and dirt from previous takes.
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.
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.
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.
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: In the credits, Michael Myers is said to be 23. However, the fact that he is supposed to be 21 in both films (because #2 took place directly after the first) is stated in both movies.