Given the complex and time-consuming nature of shooting a feature film, most projects have already been planned out to a highly meticulous degree weeks before principal photography actually begins.
Shot lists are devised, storyboards are inked, and in certain cases, action sequences are pre-visualised, so all that’s left to do on the day is turn up on set, stage each camera angle and get to work. More or less.
This lengthy pre-production phase means it’s easy for filmmakers to drop carefully-planted clues that hint at upcoming events in their movies. They’ve certainly got the time to do so, and they certainly choose to do so, because there are tons of cheeky winks to the audience in everything from massive blockbusters to small horror gems.
By design, they're hard to spot and easy to miss - a throwaway line of dialogue here, a simple joke there - but when you re-watch a film and discover them for yourself, they seem so obvious, the very definition of "hidden in plain sight".
So, if you never noticed these eight vital signs before, then you're probably not alone.
8. Snape Stuns The Death Eaters - Harry Potter And The Deathly Hallows: Part 2
Those who'd read the books before seeing the movies knew that Snape was actually a good guy long before Harry Potter And The Deathly Hallows: Part 2 came out, but for people who skipped the novels, the revelation of his heroic nature was a monumentally surprising moment.
Snape had behaved like a slimeball since the very first movie and had recently offed Albus Dumbledore, and as the Harry Potter story neared its end, it seemed like there was no way the character could be redeemed.
But redeemed he was, and because the truth - that Snape had been working with Dumbledore since Harry was a baby - meant that Snape had never been a bad guy in the first place, the filmmakers were forced to plant subtle, easy-to-miss clues that hinted at his true nature.
Take this one, for example. Before the Battle Of Hogwarts begins in Deathly Hallows: Part 2, Snape gets into a small skirmish with Professor McGonagall in The Great Hall. At one point, Snape deflects one of McGonagall's spells, sending it flying into the two Death Eaters stood behind him.
At face value this seemed to be Snape just acting like a selfish tool (since he'd rather let his fellow bad guys eat the spell than take it himself), but it's actually the opposite.
He sends that spell flying at the Death Eaters on purpose, in order to subdue them before they can attack any of the students, Professor McGonagall, or, indeed, Harry himself.