Factual error: Most ventilation ducts are not large enough for a person to crawl around in, and any duct large enough for an adult to fit in wouldn't be able to support the person's weight. In the rare event that a company could afford a large ventilation system that could support a person's weight, they would likely forgo it anyway, as it would pose a security risk.
Common movie and TV mistakes
This is a list of mistakes, things done wrong, etc. that happen so frequently onscreen we barely notice any more. 'Movie logic', stupid behaviours, and everything related.
Factual error: Enhancing an image by zooming in to blurry CCTV footage and somehow reading the reflection of a ticket in someone's pocket off a nearby fridge.
Deliberate mistake: In fight scenes, it's often one person against a small army. Despite having the person greatly outnumbered, the enemies proceed to attack them one at a time, allowing each to be easily dispatched. The whole point of having so many is to overwhelm your enemy... not take turns getting punched out.
Character mistake: In almost every film or TV show, if the villain actually bothered to kill the hero as soon as they met face to face instead of just talking about their plans, the villain would actually succeed in his or her plans. Instead, the villain letting the hero live becomes their real downfall.
Factual error: People being in a vicious gunfight with no ear protectors and still being able to have a normal conversation afterwards.
Factual error: True gun silencers do not exist in real life. There do exist what are called "suppressors," but they don't quiet the sound of a gunshot anywhere near what you see in movies and television shows.
Factual error: Airbags which deploy and stay inflated. That's not how airbags work, they deflate immediately.
Character mistake: People who run after cars when they drive away expecting to catch up with it on foot.
Upvote valid corrections to help move entries into the corrections section.
Suggested correction: Generally, people aren't thinking too forwardly or rationally when someone they're pursuing is about to get away. Their lizard-brain just thinks "getting away -> chase," not considering how unlikely (though not impossible) it is for them to either catch up with the car before it fully accelerates or when it makes a turn, then either pull the driver out of the car or jump on the car.
The person acts on instinct. Many people would do the same in real life.
Revealing mistake: "Hacking" something by hammering a keyboard and characters appearing they're nowhere near actually typing.
Audio problem: Non-metal items making audible metallic sounds. The audible metallic sound effect of a blade, such as a sword, when it's being drawn from a wood or leather scabbard that doesn't have a metal throat, and also when it's drawn from a fabric or leather belt.
Other mistake: When someone is working on a car or changing a wheel they always manage to keep their hands clean.
Factual error: When a police officer finds a suspicious powder he or she puts some on his or her tongue and knows straight away what drug it is, in reality the powder would need a lab test to analyse it.
Upvote valid corrections to help move entries into the corrections section.
Suggested correction: Not true. Generally they are tasting it to see how pure the drug is. Hard drugs are often diluted with milk sugar, so they make a bigger profit. The higher the sweet taste, the less pure the drug is.
First, law enforcement officers don't ever taste drugs, it's a good way to die if you don't know what you're ingesting. But second, the mistake isn't saying they are tasting drugs to know it's strength or purity. The mistake is explicitly about a cop tasting a drug and positively identifying what it is based on taste, which happens a lot in cop movies. Such as when the cop says "that's cocaine", not "that's half pure cocaine."
Factual error: In many films and TV series that feature passwords being cracked by a "brute-force" attack, individual characters of a password are found independently of each other. (See Ocean's Eight, Under Siege 2, various episodes of Alarm für Cobra 11 - Die Autobahnpolizei, or Person of Interest.) In reality, this is impossible; most of the times the password itself is not stored anywhere. Rather, an irreversible cryptographic hash of the password is stored, and the typed password's hash is compared with that. Either the whole thing is right or no access is granted.
Factual error: Snipers using a laser mounted to their rifle to line up their target. Snipers in real life don't use lasers in this manner. For one thing, it gives away their position, and additionally because lasers won't line up a target accurately at a long range, as the bullet is affected by gravity, the rotation of the Earth, and other factors.
Other mistake: There is always a parking space available right in front of the building where the hero/cops/protagonist needs to go.
Deliberate mistake: Characters in super hero movies commonly wearing only a small mask over their eyes which somehow keeps people from identifying them. Despite the fact that most of their facial features and hair styles are visible and recognizable. Great examples being Robin, Green Lantern, The Lone Ranger, and The Incredibles. And of course Superman just takes off his glasses.
Factual error: Babies being born and looking a) much older than newborns, b) not covered in blood and gunk, and c) perfectly normal skin colour. Often no mention of cutting a cord or delivering the placenta either.
Factual error: Someone gets punched in the face or otherwise knocked out and comes around hours later, then goes on to pick up where they left off as best as possible and forget the incident in about 30 seconds. If you've been unconscious for hours you've got a traumatic brain injury and need medical attention, you won't be hunting down your assailant any time soon.
Other mistake: A common error for Batman films, despite Gotham City being a large and heavily populated city akin to New York or Chicago, Batman never gets stuck in traffic. In fact, whenever Batman is shown driving through the streets of Gotham, there is little to no traffic at all.
Deliberate mistake: You don't automatically get "one phone call" when you're arrested in the USA. Depends on the state, for a start. You're always entitled to access to a lawyer regardless, but not always making the call yourself. If you make a call with no-one answering, you've not "wasted" your call either. Plenty of states allow multiple calls, within reason. It's a plot device, not based in reality.
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