Yep, just like in Who’s Afraid of Virginia Woolf?, the apparently miserable couple whose long marriage no-one can understand is entirely founded on their mutual denial of the loss of the one good thing they ever had. Although that doesn’t explain why they imagine him to be an Ambiguously Gay, profligate wastrel…

• Granted, it would present a challenge for a ghost to use the telephone.
• Well, in the Swedish novel The Dung-beetle Flies at Dusk the kindly old lady who has periodically been phoning up the protagonists with helpful if slightly cryptic hints turns out to have been Dead All Along…
• Perhaps every now and then someone about his age, or who sounds like him, calls up ordering Chinese food. Hearing their voice causes Richard and Hyacinth to slip into denial and start talking to them as though they were their son, leaving a very confused person on the other end of the line. Perhaps when he was alive they fought over the fact that he was wasteful with money and could never accept the fact that he might be gay. Now they just imagine him always asking for money so they can always send it to him and always dropping hints about his sexuality so they can always “accept it” as a way to assuage their guilt.

Keeping Up Appearances shares a universe with Rumpole of the Bailey and Hyacinth is actually Hilda’s niece

This is inspired by a couple of observations. Firstly, the first time I saw Peggy Thorpe-Bates with a particular haircut and from a particular angle I mistook her for Patricia Routledge (there’s an age difference but the episode of Rumpole was made several years before Keeping Up Appearances).

Secondly, the characters do have some significant character traits in common. Both call their father’s “Daddy” in a near identical tone of voice. Both are stern-voiced social climbers whose major obsession is to get their husbands, who have no social aspirations, to greater social positions.

Also, while Hilda’s family certainly seems to have more money than Hyacinth’s, the differences are no greater than those between Daisy/Rose, Hyacinth and Violet.

The sisters’ maiden name was “Bouquet”.

This would explain the floral theme to their names. Also, when Hyacinth and Richard got married, it would allow her to use the “bouquet” pronouncation even though she is now Mrs Bucket.

• Jossed by the prequel Young Hyacinth, in which it is revealed that the sisters’ maiden name is Walton.

Hyacinth insists on pronouncing her last name name as “Bouquet” because that is how it’s supposed to be pronounced

• Hyacinth looked up Richard’s genealogy and found that he’s of Norman or Huguenot descent, so it’s not just out of pretentiousness that she insists on the bouquet pronunciation but rather a different form of snobbery.

Hyacinth’s continuous social climbing is the result of that being the only way of life she has known.

• The prequel shows that Hyacinth was raised in a poverty-stricken household, so she kept aspiring to live a more affluent lifestyle. After she married Richard, she managed to pull herself up to a comfortable middle-class lifestyle; for a while, that satisfied her but after seeing how much better off Violet is living (at least in material terms) she became jealous and realized that her current lifestyle wasn’t enough and now she aspires to become part of the upper class. If she and Richard do somehow manage to become wealthy, then she’ll be jealous of people with titles, those who come from an old money background, or the ultra-wealthy.

Daddy molested his daughters when they were children and their collective dysfunction as adults is the result.

• Yes, this is super dark and off putting. But Daddy is clearly a sexual predator, given even in his extreme old age he’s constantly harassing and groping women. Him preying on his daughters in their childhood could explain why they all turned out so oddly. Hyacinth is in extreme denial and is ultra obsessed with living a “proper” kind of life (yet constantly makes excuses for why she doesn’t want Daddy to live with her or to even be around him that much), Rose became hypersexual, Violet picked a spouse who’s clearly gay or maybe even trans, and Daisy coped with it best, but still does nothing to pull herself out of abject poverty or even clean her immediate surroundings, which are filthy (a definite sign of depression).