Making a movie or a TV show is no easy feat. In fact, it’s a huge undertaking that takes time, money, cooperation, meticulous planning, and a careful knack for detail. From the screenwriter who molds the initial idea to the actors who bring the message to life, countless people are involved in the process. But as you can see in this list, even the most detailed preparations sometimes can't spare motion pictures from a fair share of cinematic blunders and gaffes.

To learn more about movie mistakes, the reasons behind them, and how studios try to get away with them, we reached out to Michael W. Boyce, Ph.D., a host of a podcast called Geek 4 that’s all about fans, fandom, and fan cultures. Being a Professor of English and Film Studies at Booth University College in Winnipeg, Canada, he explained that filmmakers leave these goof-ups in their work mainly due to financial reasons.

"Movies are incredibly expensive to make, and are sometimes shot in ways to suit actors’ schedules so making sure every detail is consistent is really hard," Boyce told Bored Panda.

"At times, shots in the same scene are filmed months apart. While there are people whose job it is to ensure continuity, mistakes happen: a child wears a digital watch in a crowd scene (Glory), an extra’s broom doesn’t touch the ground (Casino Royale), or, and one that became worked into cannon, a stormtrooper bumps his head (Star Wars: A New Hope)," the professor added.

It looks like movies and TV shows are absolutely rife with these mishaps, otherwise known as "continuity errors" — something that breaks the audience’s attention by shattering the illusion that the movie picture is seamless. Like this example where Julia Roberts eats a pancake in one scene, and a croissant in the next. When viewers take notice of these mistakes, they may feel confused and get distracted from the story itself.

"The editor’s job is to make sure that any breaks in continuity are invisible enough that they do not disturb the audience’s involvement in the story," Norman Hollyn, a professor of cinematic arts at the University of Southern California in Los Angeles, told Inside Science. "We use many different techniques to disguise these mismatches and distractions and we use the fact that, like magic, audiences tend to be distracted by differences in size, color and movement."

So when observant cinema detectives note and expose the slip-ups that creators hoped would go unnoticed, it brings them a sense of pleasure. "I think it’s a matter of rewarding people for spotting something that other people don’t notice," Boyce told us.

"When we notice that someone’s tie changes color, or someone’s drinking glass magically refills between shots, we’ve caught something we’re not meant to notice and which most people aren’t aware of," he added. "I think some people enjoy that kind of secret knowledge, whether to feel like they’re a better audience member than for noticing the minutia of a scene or that they’re a more avid fan of a film."

Interestingly, a study conducted by researchers from the University of Tokyo, Japan, found that synchronized blinking stops viewers from missing the action. It turns out that we subconsciously time our blinks while watching films to ensure we won’t miss anything important. Because of that, moviegoers even tend to blink in unison.

Tamani Nakano, the co-author of the study, told NewScientist that the flow of visual information to the brain is halted by up to 450 milliseconds with every blink, and we lose up to 6 seconds of information every minute. In their experiment, volunteers either watched a silent comedy with a strong narrative, a movie with no narrative, or listened to an audiobook. Then they measured whether the volunteers’ eye blinks happened at the same time. They found that in some cases, individuals will blink simultaneously while watching the same film.

"We all commonly find implicit breaks for blinking while viewing a video story," Nakano said. "The blinks may form one external manifestation of that, which may provide a window into understanding what people are thinking when they watch a movie."

However, even if we try our best to pick up every detail on the screen, mistakes sometimes slip through our eyes. Sometimes because our attention is focused on making sense of the things we are watching at the moment. But other times, it’s because of the way a movie or a TV show is shot and cut. When asked whether filmmakers try to distract us from these flaws, Boyce said, "I am sure that there are some mistakes left in because filmmakers assume the action of the scene will distract the audience from the mistake."

"In Hitchcock’s North by Northwest, a child extra covers his ears before a gun goes off in a busy restaurant. Everything happens so quickly, only the most eagle-eyed viewers would have caught it on a first screening."

Looking for blunders in your favorite movies or shows can even become an entertaining activity to do with friends or family. So if you are interested in trying to spot these types of errors, Professor Boyce was kind enough to share a few suggestions: "Watch for drinking glasses and food. The volume of liquid in a glass and the amount of food on a plate are really hard to match perfectly shot to shot. Clothing is also a common source of errors – ties change color, sweaters appear and disappear."

"But mostly, watch extras and background actors. They’re not supposed to be the focus of a particular scene and their mistakes are often left in films because they’re not the focus and it’s too expensive to reshoot a crowd because one person did something wrong," Boyce concluded.