10 Obscure Movie Secrets That Took Years To Discover

2. Riddle's Stones - Harry Potter And The Half-Blood Prince

The level of detail that went into the Wizarding World is still astonishing and Warner Bros' greatest success in the movie franchise was thanks to them commiting to the same sort of attention.

Crucially, the film-makers also added their own little touches and it was one of those visual clues in Harry Potter And The Half-Blood Prince that one eagle-eyed fan only noticed a little under 9 years after it was released to cinemas.

For the sequence in which Dumbledore visits a young Tom Riddle at the orphanage, one close up shot shows that the boy has meticulously lined 7 pebbles on his windowsill, not only foreshadowing his seven Horcruxes but also offering a hint of the location of one of them (the locket in the cave). The stones appear to be mementos of the seaside trip that Riddle cherished enough to choose the cave for the hiding spot.