Continuity mistake: At the start when Jimmy opens the fridge door there are quite a lot of items in there. If you look to the right of the beer bottles on the lower shelf there is nothing but a purple box. In the next shot when he starts to take the beer out of the fridge you see that on the lower shelf beside the beer bottles there is a red object. (00:04:00)
Continuity mistake: Jimmy opens the fridge. On the second shelf there are no packages of lunch meat. A few seconds later a pack appears, and shortly after that 4 more appear out of nowhere. (00:04:10)
Continuity mistake: When Sarah is injured and riding up in the dumbwaiter with Charlie's dead body the position of Charlie's head changes significantly between shots. (00:59:57)
Continuity mistake: Near the end of the film Keri/Laurie stabs Michael with a flag post through his chest and when he falls over his mask is different and his knife is much bigger. (01:09:15)
Continuity mistake: Just before Michael stabs Laurie you can already see the injury make-up applied to her arm as she swings the axe at him. (01:10:39)
Continuity mistake: When Jamie Lee Curtis is teaching a class, just prior to the class trip, a shot over her shoulder shows on the blackboard 'W.B. Yates'. It should be spelled 'Yeats'. In a shot a few seconds later the spelling has been corrected.
Continuity mistake: When John dives out of the window after first seeing Michael, there is no way he can land on his feet. He dove out head first.
Continuity mistake: More than one mask was used in the film. This is most noticeable as the look of the mask changes from time to time.
Continuity mistake: In one scene, Jamie Lee Curtis takes a bottle of something out of the fridge, removes the top of the bottle and takes a drink, then hands the bottle over to her new boyfriend, he also takes the top off the bottle, even though it was never replaced - Jamie Lee Curtis can be seen playing with the top in her hands.
Continuity mistake: When Jamie Lee Curtis goes back into the school with the axe and Michael Myers is hanging on to the pipe you can see she has a cut on her arm. When Michael comes down he stabs her in the spot where the cut was - you can clearly see it has disappeared.
Continuity mistake: When the mom and the little girl go into the men's room, the mom blocks the door with a rock. If you look closely the rock changes angles from shot to shot.
Continuity mistake: There was supposed to be a loss of power inside the house in the beginning, but Jimmy opens the fridge and the light comes on.
Continuity mistake: When Laurie Strode goes back into the school to battle Michael with an axe, she strikes him and it sticks in his shoulder. In the next shot you can see it's only left flat on his shoulder.
Continuity mistake: In the montage scene with the newspaper articles and etc. there is a shot that says "Class of 78" and Laurie Strode - Laurie would have graduated in '79 if she was a senior during the first Halloween, since it was October of '78, and graduation would have been the next year.
Continuity mistake: At the end, Jamie Lee Curtis has two kitchen knives and continually stabs Michael until he falls off the balcony and onto a table. You can obviously see that it's a dummy because the dummy falls on its side if you look closely the right side of the table collapses, but then they switch to another shot with a real person and it now shows the left side of the table has collapsed.
Continuity mistake: When Kerrie comes back from lunch with Adam Arkin she is in the car with Josh Hartnett and Adam. She turns into the school driveway and it clearly shows that her window is up but in the next shot when she calls for Ronnie her window is down.
Continuity mistake: When Jamie Lee Curtis hits Michael Myers with the van and they go over the cliff, you can see that the back doors of the van swing open, but when they get a frontal of Jamie going down the cliff in the van, the doors are shut, this happens about 3 times before the van finally stops.
Continuity mistake: When Sarah is fleeing from Michael, she gets into the delivery vehicle with Charlie, who is dead. His eyes are open, but then they are closed.
Continuity mistake: When Will and Laurie are in the hall, it is Michael who comes up the stairs, as you can see the mask and hair. It's not until they cut away to Will and Laurie, then back again, that "Michael" becomes LL, and gets shot.
Continuity mistake: In the yearbook photo of Laurie it says class of 78. She just started her senior year a few months earlier, so she would be class of 79.
Chosen answer: There is no answer to that. Its simply bad work by the writers. They never tried to explain that. You could perhaps assume shock had prevented the paramedic from immediately taking the mask off. Unlikely though,.