The first appearance of Molly Weir as Hazel the McWitch, a character who would become a regular the following season. However, for her two season four appearances (here and in episode 4.4) the character's name is spelt as "Macwitch", not the more familiar spelling which would be instated from season five onwards.
The first time that Ann Emery is credited with the name "Ethel", rather than "Mrs. Meaker" in the end credits. However, her onscreen husband wouldn't be credited as "Harold" until the sixth series.