The opening scene of the movie, though simulating one continuous take, was comprised of three separate takes spliced together, resulting in some continuity errors.
- In the opening scene, the clock above the stove reads 9:25 and the clock on the wall reads 9:40. Shortly afterward, the clock chimes ten times – indicating it’s now 10:00. When six-year-old Michael is walking down the stairs, the clock on the wall shows an even later time.
- The pile of clothes in Judith’s bedroom change from being balled up before Michael puts on his mask to being strewn about the room after Michael’s stabbed Judith.
- When Michael exits the house, you can hear the clicking of the door closing behind him. In the wide shot, the front door is wide open behind him.
Though the film is supposed to depict a fall day in the midwest, the film was notably shot in California in the spring and can be picked upon several times through the film.
- The rocky mountains can be seen both in the scene of Michael stealing the car and when Loomis is at the rest area phoning Haddonfield. Illinois has no mountains.
- Palm trees can be seen during the shots of Laurie and Tommy walking to school; palm trees do not exist in Illinois.
- Several of the cars in the film show California license plates compared to Illinois license plates.
- Though the filmmakers made an effort with having fake leaves blown throughout the film in the wide and medium shots, several close-ups of the characters throughout the daytime scenes feature no such occurrence. This is most prevalent when Laurie is waiting for Annie to pick her up.
- In 1978, Halloween was on a Tuesday. Lynda mentions a football game that night. Later, when Laurie and Annie are discussing Ben Cramer, Laurie mentions having to call him tomorrow. November 1 would’ve been a Wednesday, and – at the time – Laurie would’ve seen him at school.
- Daylight savings time would’ve been in effect during Halloween, and it would’ve been dark by the time Laurie was picked up by Annie.
The exteriors used for the Doyle and Wallace residences were not the same as the homes used for the interiors.
- In the Wallace house, the doorway is already completely to the right of the home. However, whenever anyone enters the Wallace home, the doorway has changed to the left of the home and everyone travels right to go anywhere.
- The Doyle home’s door has the knob on the right side both on the inside and the outside of the home.
- In the 2013 commentary track, even Jamie Lee Curtis talks about this a few times.
- The front door of the Doyle home is a French-influenced door when Laurie first gets dropped off, before changing to the door that is seen for the rest of the film.
- The window sizes in both homes frequently change sizes depending on if you’re looking at the home from the outside or the inside.
- Early on, Laurie says the homes are three houses down from each other’s. In the film, they’re across the street from one another.
Elsewhere, the following continuity errors are presented in the film.
- When Marion struggles with Michael in the car, a wrench can be seen taped to Nick Castle’s hand to break the window. When he stalks Tommy later on, that same window is no longer broken. Additionally, the sounds of tires screeching can be heard throughout this ordeal. However, it’s raining outside and the roads would be wet.
- Laurie sees Michael at several points during the day – outside her classroom, her bedroom window, the brushes on the walk home from school, and when he drives past her, Annie and Lynda. In each shot, he is already wearing his white mask. However, later on in the film, Laurie and Annie drive past the pharmacy where Michael’s supplies and masks were stolen from, implying it’s a fairly recent ordeal.
- This continuity error was something that was corrected in Rob Zombie’s remake from 2007. In his commentary track, Rob Zombie talks about filming the daytime scenes with two different masks and even without the mask depending on what order they settled on placing scenes in.
- Laurie, Annie and Lynda’s walk home from school was clearly taped throughout the day and comprises different takes put together. The position of the sunlight changes throughout the scene, and the ground goes from being dry when they’re walking home to being wet when Laurie bumps into Sheriff Brackett.
- Annie’s underwear changes from a solid colour inside the Wallace home to having a floral print in the laundry room.
- Inside the laundry room, the lock on the door is unlocked when the door closes. When Annie tries to open the door, the lock is clearly engaged – actress Nancy Loomis had locked it while blocking it from the camera.
- After Paul calls asking for Annie, Lindsey Wallace clearly hangs up on him. When they return from the laundry room, Annie continues the phone call without calling him back.
- The van door is left open when Bob and Lynda make their way inside the home. However, when Laurie passes by it later on, it’s been closed.
- Right before she dies, Lynda dials the Doyle residence without looking at the phone. However, it’s a rotary phone; she most likely would’ve needed to look to make sure she was dialing the correct numbers.
- In both this film and several of the sequels, Judith is referred to as having been 17 when she died in the opening scene. However, the tombstone displayed above Annie shows her dying just ten days short of her fifteenth birthday.
- Laurie leaves the bedroom door wide open when she first discovers the bodies of her friends. When she runs out into the hallway, however, the door is only partially open.
- After unlocking the door in the kitchen to get to Laurie, Michael starts to push the door open. In the next shot of the door, he is re-opening it. Additionally, the fake glass pane is obvious compared to the real glass panes in the door that Laurie escapes from. That same glass pane disappears in the shots of Laurie escaping from outside the house.
- The positioning of the pillows on the bed in the final confrontation change between Laurie entering the bedroom and after she’s knocked Michael out with the hanger.
- The clothes in the closet change looks and position depending on the shot used during the closet attack. Additionally, Laurie goes from grabbing a wire hanger to stabbing Michael with a white-coated hanger.
- The final shots of the film are supposed to represent how everything looks after the attacks. However, the shot of the Doyle living room shows the knife on the floor. By that point, it should be upstairs in the master bedroom.