There's probably no movie in existence that doesn't have at least one little mistake in it - the nature of even the simplest film production is so complex and multi-faceted across countless different departments that it's practically impossible for everyone to account for everything.
These mistakes can be great fun for enterprising audiences to spot, but at other times they're just downright weird, embarrassing, and even on occasion a little bit disturbing.
These 10 films, some of them even certified cinematic classics, all contain head-scratching screw-ups, from visual effects gaffes to mind-blowingly obvious continuity errors, and even a most unsightly wardrobe malfunction, each of which left keen-eyed viewers wondering quite what the hell they'd just seen.
These mistakes may not sink their respective films, but they're definitely odd enough to generate a whole new dialogue about each film's production - namely, how did these mistakes happen, who was actually to blame, and does the director know about it today?
There have certainly been far more egregious and offensive mistakes in the history of film, but they really don't get much odder than this lot.
Credit to the fine folks at /r/MovieMistakes for stumbling across some of these choice flubs...
10. The Face-Morphing Winklevoss Twin - The Social Network
Even a director as absurdly meticulous as David Fincher can't get everything right 100% of the time, as evidenced by this peculiar oversight in his phenomenal drama The Social Network.
One of the film's greatest triumphs is the visual effects coup of having Armie Hammer play both Winklevoss twins, Cameron and Tyler, and because Hammer wasn't particularly well-known in 2010, many simply assumed that twin actors were hired for the gig.
Instead, actor Josh Pence played Tyler's stand-in on-set while Hammer played Cameron, and Hammer's face was later digitally mapped over the top of Pence's. It's a practically seamless effect, save for just a single scene.
When the twins approach Mark Zuckerberg (Jesse Eisenberg) to work on their website early in the film, Josh Pence's face is actually visible at both the start and end of the scene for about a second each.
Pence looks similar enough to Hammer that it's not immediately obvious, but once you do notice it, you'll never not.
Quite how these shots simply didn't render Hammer's face is anyone's guess, yet they incredibly managed to slip past even a strident perfectionist like Fincher.