The quantum energy particle created in her laboratory by Professor Moffat in "Heist Society" is named "Centurium 21". Century 21 was the name of the production company Gerry Anderson created while filming the original 1965 series of "Thunderbirds", and the stylish Century 21 logo was first used for the "Thunderbirds Are Go" motion picture spin-off. Writer Peter Briggs used the name as an homage, and requested to the show's producer Estelle Hughes that the actor recording artists pronounce it "Centurium Two One", which was an eccentricity that Gerry Anderson affected when speaking his company's name aloud.
In this episode, reference is made to a "Spectrum Satellite". This was a further Peter Briggs reference to "Captain Scarlet", another Gerry Anderson show. ("Spectrum" was the organization the eponymous hero worked for in that show.)
Hugo Hallgren, the Scandinavian driver of the Reykjavik Express in the show, is voiced (uncredited) by David Menkin, who also supplies the voices of Gordon Tracy and Virgil Tracy in the episode. David Menkin is himself Norwegian-born.
The character's name came from the (then) 10 year-old Swedish son of somebody writer Peter Briggs was dating.
The character's name came from the (then) 10 year-old Swedish son of somebody writer Peter Briggs was dating.