The highly complex nature of filmmaking generally ensures that a production has to be meticulously planned out to the letter, with dozens of departments successfully co-ordinating their various disciplines in order to achieve as smooth a shoot as possible.
But the sheer number of moving parts also ensures that things don't always go right, and while this can often result in scenes being reset and re-shot, in other instances filmmakers simply decide to pivot and incorporate a mistake into the film they're making.
This has certainly been true of the horror genre, where smart or sometimes oblivious filmmakers have included an accident or a mistake in the final cut of their film, and in turn only enhanced the eerie, unsettling atmosphere.
These 10 films all took full advantage of everything at their disposal to keep viewers on their toes, even taking an apparent gaffe and transforming it into something sure to leave the audience's neck hairs standing up - quite literally, in one instance...
10. A Visible Crew Member Was Kept In The Film - The Descent
Neil Marshall's brilliantly white-knuckle low-budget horror film The Descent follows a group of six women who, upon entering a cave system, find themselves preyed upon by the "crawlers" residing within.
It's an exceptionally atmospheric and unsettling movie in its own right, albeit one elevated even further by an on-set mistake which sneaked its way into the final cut.
Shortly after release, some fans reported that they could see a crawler sneaking around the caves early in the movie before they're actually introduced.
When The Descent hit DVD, the rumours were indeed confirmed, as roughly 25 minutes into the movie when the women light a flare, to the left of the frame a spectral face is briefly visible peeking from behind a rock.
On the DVD commentary, Marshall confirmed that this was in fact a total accident: rather than a crawler deliberately inserted into the scene as an Easter egg, it was a crew member who inadvertently got himself caught on camera.
The visual is thankfully just faint enough that audiences have the opportunity to see it but not quite realise exactly what they're seeing.
Within the context of the movie itself, it basically introduces the crawlers before they're officially set upon the movie's characters - accidentally, of course.