David Suchet's own father, Jack, had moved to London from South Africa in 1932. He was a doctor who had worked on penicillin with Sir Alexander Fleming.
Vernon Dobtcheff (as Simeon Lee) has appeared alongside 2 different Poirots: David Suchet here in this rendition, and Albert Finney in Murder on the Orient Express (1974).
Alternate titles for "Hercule Poirot's Christmas" include "Murder for Christmas" and "A Holiday for Murder".
When Poirot is in the shop searching for a gift for Japp, the proprietor a "Sherlock Holmes detective set" - implying that in the universe of Hercule Poirot, Sherlock Holmes is a fictional detective.
The portrait of Simeon Lee is a handsomely faithful 'rendering' of a famous oil on canvas by John Singer Sargent. The original is of Thomas Lister, 4th (and final) Baron Ribblesdale, and was completed 1902. The titles of the portrait are 'The Ancestor' and 'Lord Ribblesdale'. The portrait hangs in the National Gallery in London.