A long-running movie franchise doesn't just appear overnight fully formed, and it can take years and multiple stabs at a project before the creators find its identity.
But there are always elements which seem essential to some iconic series' long-term success; instantly-memorable staples which meant the difference between these movies invading every part of the zeitgeist or falling into obscurity faster than Solo: A Star Wars Story.
After all, can you imagine Harry Potter without its score? Mission Impossible without Tom Cruise's death wish? Spider-Man without emo Peter Parker? Actually, maybe scratch that last one.
Either way, there are some franchises you just can't imagine existing without certain key elements - which makes it all the more surprising when you return to the first instalments and realise they aren't anywhere to be seen.
9. Laurie Being Michael's Sister - Halloween 2
Though it's always the bad guys who become icons of horror franchises, they'd often be nothing without a suitable foil. None exemplify that better than Michael Myers, though, whose rivalry with sister Laurie Strode has provided the backbone for the bulk of the Halloween series.
However, perhaps the biggest aspect of their relationship - and the mythology of the franchise in general - the two enemies being brother and sister, wasn't actually a part of the initial story. In fact, the original film doesn't once suggest that the connection between the duo extends beyond Laurie being another body The Shape plans on introducing to his knife.
The familial relationship was only established in the sequel, Halloween II, instantly becoming part of horror legend and acting as the small sliver of backstory audiences actually knew about the enigmatic villain.