Revealing mistake: In the beginning when Michael crawls out of the mine shaft that was just bombed he floats downstream. You see that he floats up to the old man's dock. If you look at him you can clearly see that he is wearing a black lifejacket. The filmmakers didn't even try to hide it under his suit, it is clearly visible on the outside of his jumpsuit.
Audio problem: When Tina is in the car with who she thinks is her boyfriend but is really Michael Myers; watch her lips when she says the line "Nothing Mike, that's what I get, Nothing." It is obvious that this line was dubbed in over something else as her lips do not match that particular line. (00:42:55)
Continuity mistake: In the scene were Tina asks Michael to stop the car at the store he starts driving faster going at least 30mph for 7 seconds. When he finally stops and backs up he drives about 5-10mph and ends up outside the store in 4 seconds.
Visible crew/equipment: While Mikey is shinning his car (as well as the stage light already listed as a mistake), as he goes along the side panel, just before the side mirror goes out of shot you can see the camera go past and a guys head in the reflection of the mirror.
Continuity mistake: When Michael rams the pitchfork through Spitz, it is at the lower end of his back, nearer to his waist even. A few seconds later when Spitz's girlfriend comes at Michael with the same pitchfork, some other shots of the now dead Spitz show the pitchfork holes up near his shoulder blades, probably 6-8 inches higher than where they should be.
Other mistake: In addition to the brake lights, there are no lights at all on the back of the car when you see it driven from behind. However, you can see that the lights are on from the front of the car.