Filmmaking sure is no picnic, and even the best of intentions from the most talented people don't always lead to good results.
Yet conversely, some of cinema's most celebrated and iconic moments weren't born out of meticulous planning, but rather coincidence and a healthy dash of luck - often at the last minute.
Each of these 10 scenes, from unforgettable action beats to indelible lines of dialogue, rank among the most memorable movie moments ever - they're all perfectly emblematic of their film's overall identity.
However, they all happened through the most unexpected and fortuitous of circumstances, such that had things been slightly different, they probably wouldn't exist at all - at least not in quite the same way.
These hallmark movie scenes, above all else, are a testament to creativity under constraints - be it time, money or even a cast member's inflamed bowels in one instance.
But even so, the end result is so perfectly conceived in each case that you'd never guess they weren't the result of a writer agonising over a script for months on end...