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: 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: 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: 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.
Factual error: Near the end of the movie, Jamie Lee is speeding down a road in the coroner's van she has stolen and Michael is attacking her from the back of the van. She slams on the brakes, and he flies into the front windshield, which shatters into many pieces. Windshields are made of laminated glass, which contains a sheet of plastic, sandwiched between to sheets of glass. It does not shatter when struck.
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 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: Although I understand the fact that H20 didn't want to include the Halloween 4, 5 and 6 timeline, Michael was burnt to a crisp by Dr. Loomis in the epilogue of Halloween 2, so he should have a fully burnt body. Also Michael was shot twice by Laurie in Halloween 2... He would have at least had scars/damage to his face in H20.
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.
Revealing mistake: When Charlie turns and sees Michael after futzing with the garbage disposal, it's obvious that Michael's mask is a (rather poor) CGI creation. It looks very cartoonish and unlike the way it looks in the rest of the film. The scene was shot early in production with an original mask that eventually was tossed out for the final design when producers thought it didn't quite look right. Because Michael was in a medium-closeup shot and they didn't have time to reshoot the scene, they opted to (somewhat obviously) digitally replace the mask.
Character mistake: The newspaper article seen during the opening credits dates the Halloween murders (the events of the first and second film) as taking place in 1968, when they in fact took place in 1978.
Plot hole: Since this was to be the last Halloween movie, there is still a major plot hole with the way things went to make Halloween Resurrection. Yes, Michael switched outfits with the paramedic. In Resurrection, one of the nurses says, "Well, why didn't the paramedic say something?" She responds that his windpipe was crushed. Yes, this prevents him from speaking, but it doesn't prevent him from taking off the mask, proving it's not Michael.
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.
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.