The running gag with Three Musketeers actor William Franklyn is that he doesn't want his then-current "Schhh... You Know Who" adverts for Schweppes Tonics (1965-73) to be mentioned.
"It's a long walk from Whitstable," says Eric to Peter Cushing. The Kent town was the actor's genuine home.
Eric jokes about Peter Cushing playing Sherlock Holmes. Cushing had previously played Holmes in The Hound of the Baskervilles (1959) and the second series of Sherlock Holmes (1964).
The special was rediscovered in 2021, and broadcast on BBC Two that Christmas Day.
William Franklyn had previously appeared opposite Morecambe and Wise in The Intelligence Men (1965).