When it comes to horror, the idea is that when it comes to monsters, less is more.
In other words, the less you see of it, the more readily you're able to imagine something terrifying. For directors, it's a way of allowing the audience to fill in the blanks with whatever they find terrifying and it saves on production costs.
There's been plenty of examples through the years, from 'The Thing' right up to 'It Follows' and, most recently, Netflix's 'Bird Box'. While you never actually see the monster in the horror-thriller, there's one scene which sees sketches of it strewn across a table.
In an interview with Bloody-Disgusting.com, Sandra Bullock explained what the monster looked like - and why she couldn't stop laughing when she eventually saw it. "It was snake-like, and I was like, ‘I don’t want to see it when it first happens. Just bring it into the room. We’ll shoot the scene.’ I turn and he’s like this (growling at me.) It’s making me laugh. It was just a long fat baby," she explained.
Director Susanne Bier backed up Bullock's description, adding that "(it) so easily becomes funny."
"(Every) time I saw it, I was like this is not going to be tense. It’s just going to be funny. At first, Sandy (Bullock) was like, ‘I don’t want to see it’ because she thought it was scary. Then it was like, ‘Don’t show it to me because (I’ll laugh).’ Every time I did it, I was like, ‘Shit, that’s a different film'... Whatever those beings are, they tap into your deepest fear," Everybody’s deepest fear is going to be different from the other person. I think to suddenly take upon a concrete shape in order to illustrate that becomes weak."
Given how the movie's central premise is about not seeing the monster and avoiding looking at it, there's complete sense in never seeing it because - well - what'd be the point of that?
'Bird Box' is currently available on Netflix.