There are several signs posted about the time of the prom, all of which say from 9 - 1. (One says 9 - 1 pm, which, of course, is incorrect.) Sue Snell asks the time at the family dinner on the night of the prom and is told that it is 8 o'clock. Shots immediately before and after the dinner scene show the prom going full swing, even though it is not scheduled to start for another hour. Additionally, it would still be light outside on May 25th at 8 pm.
Billy Nolan's car is seen briefly from behind, before Carrie rolls it, and the taillights are clearly those of a '67 Pontiac Firebird. However, when the car is overturned, it becomes a '67 Chevrolet Chevelle.
When Miss Collins is pacing in the principal's office after the shower incident, she pauses in front of his desk. Carrie's blood is visible on her shorts, making the principal uncomfortable. She then continues pacing around the office and the blood disappears. Although she is moving, her sweatshirt would not move that much as to cover all traces of the blood.
When Carrie is pleading for help in the opening shower sequence, she grabs Sue Snell's arm twice. Both times, Sue dodges and pushes Carrie away. In both pushes, Carrie grabs the same spot and Sue ends in the same position, revealing that the two pushes are the same push shot from different camera angles.
When Miss Collins begins calling the roll, the first shot reveals a girl dressed in dark blue sitting among several girls higher on the bleachers. In the next shot, she's sitting in the front row next to Helen. But in the shot after that, she's in her original place.
In the gym scene where the girls are told about getting detention or refusal of their prom tickets, Chris' lip gloss disappears and reappears. When she takes the gum out of her mouth she has lip gloss on. It then disappears and reappears as the scene goes on.
When Carrie tells Margaret about the prom, she throws her drink in Carrie's face. This snuffs out two of the candles and significantly darkens the room. A few seconds later, Margaret stands up and the kitchen light behind her is suddenly turned on, lighting up the room.
When Miss Collins is calling the roll in the gym, there are fourteen students present. When they are serving detention on the athletic field, there are only thirteen. It's possible one of them skipped the detention, but this is never specified.
When Carrie's upstairs breaking her mirror, the scene switches to Margaret White downstairs at the sewing machine. She is sewing a black dress, but the thread loaded on the sewing machine is bright red.
Chris is trying to convince Billy to help her prank Carrie at the same time that Sue is trying to convince Tommy to take Carrie to the prom. At this point, Chris has no way of knowing that Carrie is going to be at the prom at all.
In the opening shower scene, all the girls who are toweling their hair dry have obviously dry and permed hair and are just going through the motions. Also, the girls who do have wet hair before during the opening credits suddenly all have dry and nicely styled hair when Carrie starts to panic.
When Chris is about to swear at Miss Collins, it's clear from her mouth movements that she actually says the word "ass", but this is inaudible on the soundtrack. Chris appears to awkwardly cut off her own sentence, then stands there doing nothing until Miss Collins gets close enough to hit her.
When Carrie goes to kill her mother, she impales Margaret's wrists with knives through her palms. When she dies moments later, her body remains completely upright. Her body would sag, and the knives could not hold up the weight of her body. This was a deliberate decision by the filmmakers and it is mentioned in the special features in the DVD. Her death is deliberately meant to mimic the St. Sebastian statue in Carrie's closet, pierced by the arrows.