Other mistake: In the beginning of the film above the box office the date says April 12. When Sidney looks at her watch the next morning it's not even close to that date. (00:00:35 - 00:12:55)
Suggested correction: The mistake is correct, but the watch part has nothing to do with the incorrect date. It is the next day.
Revealing mistake: When the killer attacks Sid's bodyguards, the younger one has blood on his throat before the killer slashes it.
Suggested correction: That's because Ghostface smashed the window before slashing the cop's throat; it's obvious the cop got cut by some of the broken glass.
Plot hole: It is highly unlikely that the murderer knew Phil was going to put his ear to the stall when he heard the babbling. It is even more unlikely that the murderer is going to get him on the first stab through the stall. (Which also requires a lot of strength). We also have to assume that he spent time hanging out in the bathroom knowing Phil would go there to begin with, and that other two men with weak bladders were doing the same simultaneously forcing the victim to go to the stall to begin with. (00:07:45)
Suggested correction: The killer is incoherently whispering in a strange way in the adjacent stall to lure Phil to press his ear up against it. After stabbing him through it, the killer inspects the knife inquisitively, as if checking to see if he actually got him. While it's still not a terribly plausible scene, the killer's demeanor suggests that he encountered Phil in the restroom by coincidence and improvised the kill, rather than anticipating all of Phil's actions as part of a perfectly executed plan.
The general logistics and planning of the murder are a separate issue - because no, the murder was planned. The entry just says that it's "highly unlikely", putting it mildly, that the killer could guess the exact position Phil would pick to listen to the noise. Just a few inches up or down, left or right, make a huge difference. The killer looks at the knife admiring the results, because if he had any doubts that he got his victim, he'd be trapped in a bathroom with a screaming, wounded, angry Phil and plenty people who could come and help.
To be more clear, the correction here is that Phil had heard strange talking/whispering rather than music, which makes it at least a little more plausible the killer would think he might put his head up against the wall at a certain spot. Unlikely for sure, but unlikely isn't a mistake, it's just what movies do. Phil's death was planned yes, though it stands to reason the plan was more "surveil and strike when vulnerable" and less "wait for him in this particular stall we know he'll be next to."
Factual error: When Cici is about to be killed she throws the phone onto the floor without hanging up yet the killer calls her again and the phone rings. Surely it would be engaged if she had not hung up. (00:33:05)
Suggested correction: Before she throws the phone on the floor, you can hear specifically the tone indicating that she pushed the button to end the conversation. The dramatic horror movie riff fires off right at that time so you may have to pay extra attention to pick up the sound before the string section assaults your ears, but the beep is there.
Continuity mistake: When Phil and Maureen enter the cinema, Phil puts his arm around Maureen's shoulder. But in the next shot his hand is placed on her back instead. (00:01:40)
Other mistake: Maureen gets popcorn and a coke, yet doesn't pay for it. Nor does the cashier ask for money. (00:04:45)
Suggested correction: To be fair, she asked her boyfriend for some money, he gave her a note, which she holds in hand in that scene making her order and, almost certainly if we go by the arm movements, puts on the counter. If what she ordered required no change, nothing more was needed in the exchange. It's not as if she just went to the counter, didn't have any money with her, was fully on camera all the time and got her order sorted.
Character mistake: Mrs. Loomis is crazy and does not really think things through (she finishes her speech saying "who gives a f..." and that she's untraceable anyway), however it's worth noting that when she tells Sidney the official version that the police will believe, she is wrong; she says it wiping the gun clean from prints and throwing it away, which means that the police would find the supposed murder weapon with neither Mickey nor Sidney's prints on it, and neither wears gloves. Moreover, she plans to disappear and she was prominently featured in the media coverage, so people would certainly investigate her at least as victim.
Suggested correction: I don't think that a psychopathic character acting irrationally and jumping to unlikely conclusions really constitutes a character mistake. But I do think it's also worth pointing out though that cops usually don't rely on fingerprints on guns anyway - the likelihood of finding a usable print on a gun is minuscule (only about 5%), and there's going to be traces of things like skin-oil and whatnot on it from being handled, so the cops will likely just assume it was used by someone in the room - the most likely candidate being either Sidney and Mickey. Mrs. Loomis is also using a false identity and has got surgery to change her face before, so she could likely disappear pretty easily. Real-life killers get away with disappearing all the time.
I am no expert in true crimes and forensics, I am just challenging the movie logic here (which is why I talk about the behaviour of a crazy character who is running exposition). What I get from your objection though is that the cops wouldn't be able to tell that she wiped the gun clean from prints and so that wouldn't stick out as suspicious? She didn't really change her face, since Sidney recognizes her when she gets a good look at her. Rewatching the scene anyway it's very evident that she does not really care because she simply puts her faith in the cops not being able to track the fictitious Debbie Salt, so I would be happy with a correction here, I was interested in pointing out that the whole first part about wiping the prints and throwing the gun aside does not seem to logically follow up, I take note that according to your objection using 'real science' and forensics practice it might not even be that.
