The "Pass Machine", the device in which a ghostly hand slowly reaches out from a box and snatches an offered token, is actually a well known novelty bank. It was offered during the 1966 holiday season as the Thing bank, a piece of merchandise relating to The Addams Family (1964). Copies of this bank are still available.
Other than Leo McKern, Colin Gordon is the only actor to play No 2 in more than one episode (although some of the other No 2s appear in other roles in other episodes). However, Gordon was not the original choice to play No 2 in The General (1967), and this may explain the difference in character between the No 2 in A. B. and C. (1967) who is disheveled, lacks confidence, and is bullied by No 1 and the more strident No 2 in "The General". However, the characters are united by the fact that both of them enjoy drinking a lot of milk, and also abuse technology for their own ends. The script was also altered so that Colin Gordon's character could say that he knew No 6 from before.
The voice of the person who telephones No6 when he has a power cut; on the loudspeaker above "the pass machine"; the first and the almost late arriving top hatted board members and the unseen TV director of the General's speedlearn broadcast is that of Robert Rietty.
Ian Fleming is credited as playing "Man at Cafe and First Top Hat". This strange billing is because they are in fact two separate characters. The first is a "student" in the Speed Learn history courses, the other an administrator on the project.
The only episode in which an American is seen and heard in The Village (Al Mancini) which raised the question further of who ran it.