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.
Other 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.
Other mistake: When Bud goes to check on how hot the water is, he rubs condensation off the gauges, but there wasn't anything on them to begin with.
Other mistake: When Jimmy finds Mrs Alves, he has to walk through the puddle of blood to get to her, but there are no footprints in the blood.
Other mistake: Jimmy the paramedic walks into the major surgery room to find Ms. Alves dead on the stretcher, the blood drained from her body. As he turns to leave he suddenly 'slips' on the pool of blood, falling back first and knocking himself unconscious. However the next shot reveals that the blood pool extends out to the doorway, so there's no way he could have crossed to the stretcher without slipping in the first place while entering the room.
Other mistake: After the two doctors and the sheriff pull up in the parking lot and then enter the hospital, Michael suddenly appears to Laurie, and she runs from him across the lot toward the same entrance, and suddenly the doors are locked. There is no way this would be, as the doctors and the sheriff would have had to stop and unlock the entrance before entering themselves, which they did not do.