One regarding the ending twist; If Opal is actually Claire, why does the grandpa not recognize her smell? Because smoking damages your lungs and your sense of taste, both vital things to be able to smell things with any consistency.
In the beginning scene where Opal is dancing with the burger, she initially picks up the burger with her right hand, but is almost immediately shown holding it in her left. Animation goof, or A Glitch in the Matrix? Doubly so since the first moment we see her holding it in her left hand is when she and her "family" almost perfectly mimic the family on the billboard, where Opal is holding the burger in her left hand.
She can't eat the burger without poking holes in her fantasy. She doesn't have it because it's food, she has it because Claire is pretending to be Opal, the girl on the billboard. Right before she does her burger dance, her mother encourages her to do the thing... and then Claire dances and ends with brandishing the burger while the family looks on. She's re-enacting the billboard ad. And it says a lot about her state of mind that her imaginary mother has to psyche her up for her to get enough confidence to just pretend to hold a hamburger. This poor kid..
The respective songs from the Grandpa, the Dad, and the Mom reflects how Claire views her family:
Grandpa's song is low pitched and slow build to tension—— Claire's constantly on edge around him and it could be anything that sets him off.
Dad's song is gentle and calming, like one of those lullaby musicboxes, except a bit more ominous—— Claire's unnerved by him, but, betwixt the Grandpa and Mom, he's the safest to be around.
Mom's song is strange, disjointed, unclear, and "wavy-ish" but initially starts off tense——— Claire is aware of Mom's instability and feels accordingly. She doesn't want to be around her but, at times, can't get away.
Tyin' into that, we get the alternate in Opal's world and how they correspond in the real world:
Opal's Grandpa just says "Hi Opal!" and waves at her, as he can see her. (Claire's grandpa is blind)
Opal's Dad says "That's my girl." (Claire's Dad is the safest to be around)
Opal's Mom doesn't have hands where Opal or the viewers can see them. (Claire's Mother is implied to be violent)
OPAL premiered in October of 2020. What's the birthstone for October? Opal.
Opals are considered a precious gem. There's irony in this, as Claire's family doesn't regard her as being "precious".
Unlike SHOP: A Pop Opera, OPAL is animated entirely in claymation (barring the musical segments). Considering how most of Jack's work with MS Paint is usually full of bright colors and used for more comedic videos, it makes sense for Jack to avoid using MS Paint on a short about Abusive Parents and Escapism.
The opening, where Opal is irresistibly drawn to the attic, can be read as Claire instinctively knowing that living in her fantasy world where her family loves her and treats her well isn't healthy, and that returning to reality is probably the right thing for her long-term. Through this lens, the ending is even sadder, because, having opened herself up to the real world and been punished for it, Claire is now retreating into fantasy even harder.
While also, possibly, Fridge Brilliance, it's implied that Grandpa is Claire's maternal grandfather, considering the addiction tendencies and the heredity related to those. On that subject with the Grandpa, his vision problems might've been possibly caused by Diabetes II, considering his weight. Or perhaps all the nicotine from smoking so many cigarettes made him blind.
What happens when the billboard is taken down? It won't be up forever, and the advertising agency won't be aware that it's the only thing keeping a neglected little girl something resembling sane.
She'd either A: eventually find a new form of escapism, B: Fully Break, or C: Do the unthinkable
As pointed out by one YouTube comment, when Opal/Claire is with her billboard family, her face is slightly plumper and smooth looking, her hair is more blonde looking, and her hair is also thicker. But when she's with her real family, her skin is more saggy and wrinkled looking, her hair is thin and almost white, and her skin is pastier. This implies that she's so malnourished that her skin is loose on her body, and that she's also experiencing other physical health issues because of it.
The father in the intro seems very nervous when Opal sees the house across the street, sweating bullets and saying that they always tell her "Don't mind the house across the street/It's not where your attention ought to be". Once we learn that the intro was just a fantasy created by Claire to escape her neglectful real family, that scene basically becomes her subconcious pleading with her not to return to the real world because it's too much to cope with. When she does return to her fantasy, the first thing her imaginary family does is close the curtains to hide the house from view, attempting to block out her painful reality once again.
Claire is likely not getting enough food. The only adult in the house who could feasibly make a meal for her is the father, and he's unlikely to step away from the mirror so easily. The mother is in too much of a substance-induced haze, and the grandfather relies on Claire to do everything for him. It makes extra amount of sense why she fixates on the billboard, as it's not just a representation of a loving family but also a warm and delicious meal she's probably not going to get any time soon.
The father is the most capable adult here, and based on his issues it’s likely that he is constantly trying fad diets/starving himself and feeding her the same sugar-free, artificial stuff, leading to malnutrition.
One thing to note is how, in Opal's sequence, her family say "We see you.", as opposed to "We love you." The fact that Opal is actually Claire makes this worse in retrospect, as, to Claire, being acknowledged is good enough.
