It goes without saying that moviemaking is not a straightforward process.
It requires years of hard work, dedication and creative thinking, and even then, it's nearly impossible to get every single tiny detail right, which can result in an obvious blunder making its way onto the screen.
Usually, these blunders are pure accidents - with long hours and a million factors to consider, it's easy for things to slip through the cracks - but sometimes, those "mistakes" you notice while watching movies might not be mistakes at all, and have instead been put there deliberately as a result of a kink in the creative process, or just to give fans a cool easter egg to discuss.
At face value, these filmmakers and their crews have made simple errors that don't entirely ruin their movies, but might take viewers out of the experience a little, or distract them for a few minutes.
But digging a little deeper, these "mistakes" all have sound explanations behind them, and were only left in to ensure that the movie was as good and as entertaining as it could possibly be.
10. The Scratch Marks (Tarzan)
In a scene near the beginning of Disney's thirty-seventh animated classic, Tarzan gets himself into a brutal scuffle with a rather angry leopard.
As the fight progresses, the leopard lashes out at Tarzan with its claws, slashing him across the chest and leaving behind three very noticeable marks in the process.
The cuts look deep, and they definitely don't look like they'll be healing anytime soon. And yet, inexplicably - when Tarzan carries the leopard's dead body out of a pit a few moments later - the slash marks have vanished completely.
It's a miracle! A miracle of animation, that is. The mystery of the disappearing claw-marks isn't a simple goof, but a result of Disney's strict rules about what can and can't be included in their films - and blood isn't something they want to feature a lot of.
There are more examples of this in other Disney animated movies (even in this same scene, the leopard suffers a cut to the leg that vanishes), so the next time you're rewatching one of your favourites, keep an eye out for any blood. And expect it to disappear moments later.