Character mistake: When Harold is recalling Michael's 'credentials', he refers to Hilcrest academy, claiming that Michael killed four students. However, Michael only killed two; Sarah and Charlie.
Character mistake: When Tallahassee firsts meets Bill Murray, He says "six people left in the world and you're one of them." At that point they only know of 5 - the 4 main characters and Bill Murray.
Suggested correction: His character thinks there was another woman that Columbus hooked up with in the back of a FedEx truck.
Character mistake: The pilot says to his wife that the flying saucer was cigar-shaped. The actual shape was more like two dishes attached together. (00:04:45 - 00:12:20)
Character mistake: When Jackie the babysitter is stuck in the closet, she explains to George and Kathy that the door was locked. George says Amy there's no lock on this door. Her real name is Amy and her film name is Jackie.
Character mistake: When Bower is banging on Payton's hyper sleep chamber from the outside it says Payton, but when it cuts to looking from inside out, it says Bower.
Character mistake: Although Dr. Kalarjian said that there is a "code blue", which means a patient requiring resuscitation or other immediate medical attention, she wanders over there without rushing at all.
Suggested correction: When she was getting closer, she started rushing more. It took a while for her to get there but maybe that was just done to fool the audience. Kimberly did think she was going to kill Isabella after all.
Character mistake: Sid deduces that Billy could be the killer because he could have used his phone call from jail to make the threatening call. However, the deduction has to be incorrect, since if it was really Billy, he could have never used the voice-changing device.
Suggested correction: This will sound pedantic (hey, it's MovieMistakes.com, we're entitled), but I don't think this is what is meant by a character mistake. Sidney isn't presenting an erroneous fact that goes uncorrected, she's explaining an idea that had crossed her mind. Billy immediately gives a plausible response and by the end of the film it's evident who'd called her. The takeaway isn't that Billy could still be the killer but that Sidney can't help but suspect him despite their reconciliation.
Character mistake: Early in the film, Sister Paxton reveals that she wants to come back as a butterfly after she dies. Reincarnation is not a tenet of Mormonism.
Character mistake: Sir John describes St. Columbanus as a gypsy from the East, but in fact St. Columbanus was Irish and founded one of the first monasteries in Scotland (on Iona island), one of the most important in Christendom.
Character mistake: In the beginning where they are showing all the newspaper articles, the article uses Michael "Meyers" twice in one article and then back to "Myers."
Character mistake: Detective Spitzer went into Harper's dark/unlit house, saw his partner Greg on the floor, and then saw Alec standing in the kitchen. Without identifying himself, telling Alec to drop his weapon (pistol pointed toward the floor), or bothering to determine what happened, Detective Spitzky shoots Alec. (01:27:08)
Character mistake: A newspaper is shown saying "Girls Body Found" as plural when it should be "Girl's Body Found" as a possessive.
Character mistake: The reporter refers to a "box of ashes" being buried in Westlake's grave, whereas in the first film, all that was buried there was "an ear", which was all they could find of his body.
Character mistake: When Ripley asked the doctor how they "got" her, he replies from blood samples on Fury 16. This is in reference to the planet in Alien 3, but it was called Fury 161. (00:11:00)
Character mistake: The police radio identifies the fugitives' car as a 1958 Cadillac, but it is a 1962.
Character mistake: Detective Sing asks Dr Gordon to listen to Amanda's testimony. Any detective would know its not a testimony, its a statement. Testimonies are done in court, not a police station. (00:23:00)
Character mistake: There was no chance of Will and Lori knowing what's happening with Mark in the house. Neither him nor anyone else called them. So what made them rush home with van, after they've been casually driving in their previous scene?
Character mistake: During the first big battle between the Martians & the U.S. Army, the Martians use their heat ray to vaporise people and equipment. Dr. Forrester, a physicist, then quickly speculates, "It neutralises mesons somehow. They're the atomic glue holding matter together. Cut across their magnetic lines of force and any object will simply cease to exist." During the '50s mesons were theorised to hold atomic nuclei together strongly. But if the Martian rays worked as the Dr. guessed, then objects wouldn't just vaporise. They'd explode with the ferocity of nuclear weapons.
Character mistake: If the nuns in the Abbey weren't real and were created by Valek, why did Valek get one of the nuns to explain to Sister Irene the exact way to defeat her?
Character mistake: Both in the movie (and stage) versions, Mushnik makes a verbal mistake. Seymour shows Mushnik his new plant (Audrey II) for the very first time, but seconds later when the plant suddenly droops, Mushnik asks Seymour, "Why is it always wilting like that?" Always? He's just seen the plant! The line should be, "Why is it wilting like that?" Some smart stage directors of the play version have wised up and changed the line.