One word: Trauma

Rating: 8/10 (5 April 2019)

Maybe so many people missing the point of this movie is exactly the point? It's just another demonstration of how we refuse to look things directly in the eyes and call them by their names. For me this movie screams with subtle symbolism, mostly about how the human psyche works. Everywhere I look I see trauma, both personal and collective. I see the true cost of not facing and owning your darkest self, be it as an individual or a nation, and how this eventually comes back to haunt you. Just bare with me for a moment as I walk you through all the symbols.
The Tethered and the shadow:
Red introduces herself as Adelaide's shadow, they've met in the fun house which the child psychologist later on dubbed as a traumatic event. She even said Adelaide got PTSD from it, which her father dismissed with cynicism saying that she's not a Vietnam veteran. This illustrates the reality of how most of us deal with trauma, we refuse to look at it or work on it, and we do whatever it takes to just carry on. "I just want my little girl back" says the father. But trauma is a tricky thing that doesn't just go away. If you don't deal with trauma it sneaks up on you. In this case, literally.
In Jungian psychology everyone carries a shadow. In short, the shadow is the unknown side of our personalities, it's the dark part that we deny and don't identify with because of its grotesque nature. But the less it is embodied in our conscious life (so the more we deny it) the blacker and denser it becomes. And if you have unresolved trauma it also becomes part of your shadow. The deeper you push your trauma the bigger your shadow becomes and the more "power" it gains over your conscious self.
Think about Dr Jekyll and Mr Hyde, The Hulk, or werewolves tales, these stories are a perfect analogy of the shadow-self taking control over the personality in vulnerable moments. It's not a coincidence that Adelaide was wearing a Thriller t-shirt when she met Red, as she was about to meet her dual nature and experience her dark self in the form of fear. Adelaide didn't meet anyone, what she really met was her own fear, and unable to understand and cope with the fear her experience turned into trauma.
Why the Tethered decide to climb to the surface:
If you consider the above shadow theory mixed in with how trauma eventually resurfaces, this is a metaphor for collective trauma. The Tethered are our collective consciousness that we refuse to deal with. Now think about the Me Too movement and Black Lives matter for example, think about how much darkness we've shed light on in the past decade and how it has "torn lives apart" and cut things open (scissors much?). The Tethered decide to surface because it's time for the upper world to face the truth of its own choices and deeds. To face its true dark nature.
Rabbits:
Rabbits symbolise a connection between this world and the underworld. They can live both above and below the ground, in light and in darkness. The rabbits were locked in the underground world, they had no job but to be consumed by darkness (literally). But notice how when the Tethered were freed so were the rabbits. You can consider rabbits as the messengers between the conscious and the unconscious mind. The rabbits being free is the two parts of the psyche communicating again, it's a symbol of healing.
Red and Adelaide switching:
Because so much of Adelaide became Red in the fun house (so the fear/trauma/shadow) Red took over Adelaide. The real Adelaide was now locked in the underworld, or in the unconscious part of her psyche.
Jason looking at Adelaide suspiciously:
Children with their pure nature mostly see us for who we are and not for who we want to be seen. They're unbiased and honest. Think about "The Emperor's New Clothes", it was a child who pointed out the emperor's nakedness. It's also why Jason was the most in control of his shadow and the least afraid of it, he's still comfortable with this duality and doesn't see it as bad. It's why swear words don't shock him, he doesn't see them as bad just yet.
If I've decoded the symbolism correctly then Jordan Peele is one hell of a Carl Jung fan and a true master of storytelling. Being someone who had to face her own shadow (metaphorically and not in the form of a Tethered luckily), I found this movie very unsettling and somewhat true to the experience of getting to know your darkest self.