The sailor automaton in the hall is similar to a sailor automaton seen in the original version of Sleuth (1972) starring Laurence Olivier and Michael Caine, a murder mystery set in a home full of sinister toys and games.
Rachael Stirling (Eleanor Karras) is the daughter of Diana Rigg, who starred in the 1998 TV series The Mrs Bradley Mysteries (1998), which also starred Neil Dudgeon (DCI John Barnaby).
There are links to the 1972 film Sleuth (1972) which starred Laurence Olivier and Michael Caine. Not only does the action take place in a house full of games and the plot deals with the playing of games, but the made-up detective played by Adrian Edmondson at the beginning of the episode is called Inspector Doppler. This is the same name as the made-up detective Michael Caine disguises himself as in Sleuth.
Caroline Quentin (Helen Welles) and Stuart Milligan (Victor Karras) appeared together in the first 3 series of Jonathan Creek (1997). Coincidentally, Adrian Edmondson (Hugo Welles) appeared in series 4 of Jonathan Creek as Brendan Baxter, the husband of Creek's then sidekick Carla Borrego (Julia Sawalha).
Happy Families (1992) was also the name of a 1992 episode of Inspector Morse (1987). Rachel Stirling (Eleanor Karras) appeared in Inspector Lewis (2006) - the successor to Inspector Morse - in the Series 2 3rd episode Life Born of Fire (2008). Interestingly, Adrian Edmondson (Hugo Welles) appeared in a 1985 BBC comedy called Happy Families (1985). Annette Badland also starred in a 1989 BBC children's show called Happy Families (1989).