Continuity mistake: In the scene where the boys ask Mr. Hunt about Ben Tramer, Mr. Hunt says that "it's just a little past 11." Following this up in the next scene Bud lures Karen into the room to kiss her and wish her Happy Halloween. During this scene, as Bud reaches up to kiss Karen, his watch is clearly visible and shows the time as 1:00.
Continuity mistake: After getting out of the car, Laurie is on the ground beside Jimmy's car outside the hospital when she sees the Marshall's car pull up. When Loomis tells the Marshall he ought to handcuff him to the wheel, if you look, Jimmy's car is still visible in the distance, but Laurie is not in that shot.
Continuity mistake: The flashing lights on the front of Bud and Jimmy's ambulance change places as they pull into the hospital driveway. They go from either the side of the hood to the front of the bumper.
Continuity mistake: When Michael falls off the balcony, he falls into some green grass and a garden is next to him. Yet in the original "Halloween", Michael falls onto the ground with barely any grass around him, just a dirt patch and no garden in sight. (This is explained because they reshot the ending to "Halloween" 1.).
Continuity mistake: When Laurie leaves the hospital, she exits out of the hospital doors. Somehow the doors stay open. Later on in the far away shot, the doors are closed, then they are open again in the next shot.
Continuity mistake: When Michael walks into the old couple's house, NIGHT OF THE LIVING DEAD is showing on the television. At that point, the film is just beginning, with Barbara and Johnny first pulling up to the cemetery. Much later in the film, the security guard is also watching NIGHT OF THE LIVING DEAD on television, and it's the scene where the cemetery zombie is attacking Barbara in her car. This is no more than ten minutes later in NOTLD, yet it's way more than ten minutes later in the evening of HALLOWEEN II.
Continuity mistake: At the beginning of the movie, the front door lights on the Doyle house are on, then off, then on again in just a few different shots.