Professor T. tells the hotel clerk that his taxi license plate is 1729, the clerk says that 1729 is the smallest natural number that can be written two ways as the sum of two positive cubes. This is based on a supposedly true incident where British mathematician G. H. Hardy told Indian mathematician Ramanujan that the license number on his cab was "rather dull," and Ramanujan replied "it is a very interesting number" with the explanation the clerk gave. The incident is in the movie Ramanujan.
Michael Vergauwen plays Johan Vermarcke. He returns as the character in series 3.
Xandra Van Welden plays Katelijne Everaerts but returns in S2e8 and s2e12 and 13 as a different character, Marianne Termont.
Tanja Oostvogels and Bart Hollanders appeared in the same story of Callboys s2e1.
The first of only 6 stories in which the character Paul Rabet does not appear. Only Jasper, Annelies, Daan, Christina, Ingrid and Walter have appeared in every story to date.