We see them very often.
1. Camera Crew or Foreign Objects in the Frame
Viewers willingly accept the imaginary world of the movies and get disappointed when the illusion is destroyed by a crew member walking in the shot or a random thing left on set. Even multimillion blockbusters often feature crew members as unlikely characters — there are such "aliens" in Indiana Jones or Pirates of the Caribbean, for example.
Sometimes, there are also objects on the set that simply don't exist in the cinematic reality, such as the plastic water bottle in Gladiator or the coffee cup in Game of Thrones. Mirrors and glass are especially insidious since they often reflect the film crew: you may have noticed such occurrences in Twilight or The Matrix.
2. Historical Inconsistencies
Making historical movies isn't easy: filmmakers have to consider lots of nuances and details that modern viewers don't even know of. Even a largely accurate film may contain minor historical inconsistencies. Sometimes, this is a deliberate choice — as in Sofia Coppola's postmodernist film Marie Antoinette. More often, however, those mistakes are unintentional.
For example, in Dallas Buyers Club, we see the 2011 Lamborghini Aventador poster behind the main character's back — but the film's events take place in 1985! Jack from Titanic tells Rose that he went fishing on Lake Wissota as a boy, but the lake was actually formed five years after the Titanic disaster. Another example comes from the classic movie Back to the Future: in 1955, Marty McFly plays a Gibson ES-345 guitar, which wasn't produced until 1958.
3. Hero Must Hear the Villain's Plan
Filmmakers believe that the audience loves it when, at the very last moment, the hero escapes from the hands of the villain — who just happened to be ranting about his devious plan, which gave the good character plenty of time to gain control over the situation.
The technique of revealing the bad guy's plans in a long, detailed monologue has been done to death — and was also cleverly mocked in a number of modern films. For example, when the maniac in I See You starts telling the story of his difficult life, the main character shoots him without much hesitation.
4. Freewheeling 19th-century Ladies
Jane Austen's freedom-loving heroine is quite too willful for her time.
But when played by Keira Knightley, Elizabeth Bennet appears especially sassy for a noblewoman: she is rude to people above her in status, talks to men in private, and runs around with her hair down like a commoner.
5. Medical Malpractice
In medical TV series, doctors have to deal with rare diseases and complex surgeries in almost every episode — just so the show is exciting to watch. Furthermore, movie characters often do things that would make any medical practitioner's hair stand on end. Like, giving an overdosed character an adrenaline shot to kickstart the heart in Pulp Fiction?
Sure, why not. Putting a severed finger on ice in Four Room? You got it. While it's true that you should keep a severed digit in a cool container, direct contact with ice will cause tissue damage and make it impossible to reattach… Just so you know!
6. Cosmic Bloopers
Watching space movies surely is exciting. However, it may also be a pain for anyone who knows a thing or two about science. A classic example: how can we hear the sound of an explosion in space, which is a vacuum? When film astronauts return to the ship, they take off the spacesuits right away — but in reality, they'd probably pass out from a major pressure drop.
The 1998 sci-fi blockbuster Armageddon has been known as a collection of the most ridiculous space-related mistakes: the drillers don't need to put their visors down when walking on the asteroid, which just happens to have Earth-like gravity (which, obviously, can't be true because the asteroid is way smaller), and then fixing complex equipment on the spaceship requires just a couple of strokes with a wrench. Sci-fi turned fantasy, oops!
7. Timed Bombs
It's so convenient that all the explosives in action movies have a timer display with a countdown, so the hero knows exactly how much time is left before the whole place blows up. Moviegoers are fidgeting in their seats with excitement, but they have no need to worry — John McClane will stop the villain at the very last second!
8. Murderers Collecting Evidence
Obviously, they do this so that the police have something to prove they did the killings. Sometimes, as in David Fincher's thriller Seven, the maniac pins the newspaper cutouts, photos, and other physical evidence onto walls — thanks, John Doe, that's really helpful!
9. Bullet-Proof Furniture
In Mr. & Mrs. Smith, Brad Pitt and Angelina Jolie's characters have almost destroyed their house while trying to kill each other — but didn't suffer any injury beyond a few minor scrapes. That's because, in the world of cinema, all furniture comes bullet-proof and there are different laws of physics at work. Just stay behind that sofa, Angelina, you'll be fine!
10. Upside Down Phones
That's perhaps the weirdest blooper that nevertheless comes up in many popular films. For some reason, movie characters often hold their phones upside down when talking.
In Ted, for example, while Mila Kunis' character is having a phone conversation, we notice that the power button is obviously not where it should be. Any conspiracy ideas for this?