The original series ended in 1979. However a further season was made in 1996, featuring the earlier Liver Bird characters Sandra and Beryl. All of the main cast later admitted they felt this tenth run was perhaps a mistake.
In a definite sign of the times, Polly James and Nerys Hughes drank then-popular Pernod milkshakes while going over their lines.
The theme song was a version of "Liverpool Girls" (The Liver Birds) by The Scaffold, featuring Sir Paul McCartney's brother Michael under his stage name Mike McGear.
Series Creator Carla Lane confessed that Sandra was essentially based on herself, Mrs. Hutchinson was her mother, and Beryl was co-Creator Myra Taylor.
The Liver Birds lived at the second floor Flat 4 of 37 Huskisson Street, in the Prince's Park district (a genuine address located in Liverpool 8, now known as Toxteth) for the first two seasons. In the third season opener they moved to the more upmarket ground floor Flat 1, 17 Beech View in Allerton.
Co-Writer Myra Taylor left the show as, working on scripts in London, she found she was missing her family too much. A heartbroken Carla Lane wept when she left.
Although Beryl hailed from Bootle, Polly James never attempted a Scouse accent, preferring to exaggerate her own natural East Lancashire one. While Sandra was from the more salubrious Hunt's Cross, Nerys Hughes had no problem in mastering the accent, detecting a Liverpudlian twang oddly common to her own Welsh origins. Carol came from the Kirkby estate, though Elizabeth Estensen was born in County Durham.
In a stroke of good fortune while casting the new part of flatmate Carol, Nerys Hughes spotted Elizabeth Estensen in the stage play "John, Paul, George, Ringo ... and Bert", and insisted that Series Producer Sydney Lotterby also went to see her in it.
The first season was cut short owing to Polly James' workload (she was appearing in the West End, as well as filming the television show). By the time the second season was ready, Pauline Collins was unavailable, and was replaced by Nerys Hughes.
BBC Head of Comedy Michael Mills named the series, after the Liverpudlian landmarks best exemplified by the pair atop the Royal Liver Building's clock towers.
In the "Comedy Playhouse" pilot and subsequent three-episode opening series, the housemates were Beryl and Dawn. Polly James and Pauline Collins actually switched roles during the pilot's rehearsals, Comedy Head Michael Mills having assigned them the other way around.
Throughout the 1974 season, Sandra reads Leo Tolstoy's "War and Peace". In the 1975 run, she moved onto tackling "August 1914" by Aleksandr Solzhenitsyn.
Carla Lane mused that the Boswell family seen here may well be distantly related to the Boswell family seen in her later sitcom Bread (1986).
One actor and one actress from the Sandra and Carol episodes (seasons five through nine) appeared as different characters in the 1996 episodes (season ten). Carmel McSharry and Michael Angelis, who had played Carol's mother and brother, respectively, were transformed into Beryl's mother and brother in season ten.