Creator Backlash: Patricia Routledge does not approve of the Young Hyacinth prequel special, as she felt the BBC was running out of ideas by revisiting old programmes. Kerry Howard, who played Hyacinth in the special, defended it by saying that it's not a remake or reboot of the show, but a side story that rounds out the character.
I Am Not Spock: Routledge often shows signs of this in interviews given how she is a talented theatre actress and musician; however Swift is very much a straight example. In one interview to Doctor Who Magazine during his appearance in the 2007 Doctor Who Christmas special, he is quoted as telling fans of the show to fuck off if they ask him so much as a question regarding his time as Richard.
The show stopped being produced not because it wasn't popular or had necessarily run its course, but because Routledge wanted to move on to different projects and didn't want to be typecast as Hyacinth (too late).
Averted with Geoffrey Hughes (Onslow) and Judy Cornwell (Daisy) who have reprised their characters from the show over the years during fundraising drives for PBS in the US, where it remains shown weekly and quite popular.
Patricia Routledge is a musical veteran and can sing. Hyacinth cannot.
Despite Richard being shown attending church with Hyacinth, Clive Swift is actually Jewish.
Mean Character, Nice Actor: The show is often aired on PBS in the United States, and one PBS station invited Patricia Routledge over for a donation drive special. Reportedly the person that went to pick her up at the airport was terrified he'd wind up being henpecked to death, and was relieved when she was instead quite charming and easygoing.
The Other Darrin: Rose was played by Shirley Stelfox in the first series and then by Mary Millar in all later series.
Recycled Script: Writer Roy Clarke also did Last of the Summer Wine, and Edie in that show comes across as similar to Hyacinth—except that her attempt at an upper-class facade cracks far more easily.
Patricia Routledge, the actress who plays Hyacinth, is an acclaimed stage actor in a variety of genres. But watching Hetty Wainthropp Investigates where she plays a very canny detective, can be most uncanny. Especially since they seem to wear the same sorts of hats...
Josephine Tewson's previous work included assorted supporting roles in sketches on The Two Ronnies. Long after Keeping Up Appearances ended its run, she was cast as Lucinda Davenport on Last of the Summer Wine, which, coincidentally, was also created and written by Roy Clarke.
Before he was cast as Emmet, David Griffin previously played Clive Dempster in Hi-de-Hi!.
Trevor Bannister, a.k.a. Mr. Lucas on Are You Being Served? appears in the season 4 episode "Angel Gabriel Blue", playing a salesman selling kitchen tables to Hyacinth and later becomes a love interest to Rose. Amusingly, Bannister also co-starred on Last of the Summer Wine as Toby Mulberry Smith, acting alongside fellow AYBS alumnus Frank Thornton (Captain Peacock), who played Herbert "Truly" Truelove.
Norman Lovett, a.k.a. Holly on Red Dwarf, appears in the season 1 episode, "The Charity Shop", playing Mr. Duxbury, a man whose mother becomes engaged to Daddy.
In addition to his work on Keeping Up Appearances and Last of the Summer Wine, creator and writer Roy Clarke also created and wrote for Open All Hours.
Word of Dante: Patricia Routledge has stated that she thinks Hyacinth and Richard really are Happily Married in spite of his frequent annoyance with her antics, and that he does appreciate her keeping a nice house and putting dinner on the table every evening.