Dad’s Army is one of the best of those scenarios. The interaction between the characters played by Arthur Lowe and John Le Mesurier is perfectly played and written.
The IMDB page for Mollie Sugden, who passed away in 2009, says “She is still great friends with the surviving cast members…” Spooky.
Not just alive but still working from time to time, again according to IMDB.
Assuredly - and yet there was still room for several other strongly-defined characters as well. To name only one, John Laurie as Private Fraser is iconic IMHO.
David Croft was really talented as a writer, along with his co-writers Jimmy Perry and Jeremy Lloyd. I enjoyed his shows as a youngster, and to be honest probably denigrated them a bit as I got a bit older, but now can look back at them as the products of great skill and talent that they are.
Obviously he’s not around any more - what about Old Mr Grace? (I know he doesn’t get about much, these days).