It takes an actor of real composure and unique screen presence to truly leave millions of viewers creeped the hell out.
No amount of special effects can compensate for the efficient simplicity of an ice-cold stare, but sometimes actors and filmmakers alike resort to unique tactics to put audiences on edge.
These 10 movie characters all left viewers en masse feeling uneasy, creeped out, and perhaps even thoroughly terrified.
But it was more than mere acting ability that got the job done - from subtle makeup tricks to ingenious lighting techniques, and even using an actor's own apparent limitations as a tool, these characters all benefited from a sleight-of-hand that only made them more fearsome.
That's not to detract from the fine work that all of these actors put into these roles, but sometimes the most sly and subtle flourishes can be the most effective, working wonders for how an actor comes across on the big screen.
If you somehow caught any of these tricks and feats of accidental brilliance, give yourself a firm pat on the back - but you almost certainly didn't...
10. Harvey Spencer Stephens' Hair & Eye Colour Were Darkened - The Omen
Richard Donner's classic horror film The Omen is especially celebrated for its gut-wrenching unease and the note-perfect casting of four-year-old Harvey Spencer Stephens as the sublimely creepy young Antichrist, Damien.
But it isn't simply that Donner and his casting director picked a child with a piercing gaze: the production employed some sneaky help from the makeup department to ensure Damien looked as unsettlingly "off" as possible.
For starters, Stephens' hair was dyed from his natural blond colour to black, and he was also given contact lenses to darken the colour of his eyes.
These are both subtle alterations that most audiences would never even notice - especially as it was Stephens' first-ever role - but together they add up to accentuate his performance and make us unconsciously accept that something truly isn't right with this young boy.