Talking with Inspector House, Burke mentions "the case of the invisible man", a murder case he had himself solved in which the crime was committed by a postman - a figure so commonplace and insignificant that he went quite unnoticed by those watching the victim. This is, in fact, the plot of a famous Father Brown story by G.K. Chesterton, actually called "The Invisible Man".
The character of Bascule Doirot (Ed Begley) is a takeoff on Hercule Poirot.
Caligula Foxe (Thomas Gomez) is a takeoff on Nero Wolfe.
Mr. Toto (J. Carroll Nash) is a takeoff on Mr Moto.
Chief Inspector House (Carl Reiner) is a takeoff on Sherlock Holmes.
Ed Begley, Zsa Zsa Gabor, Thomas Gomez, J. Carrol Naish and Carl Reiner all receive 'Special Guest Stars In Alphabetical Order' credits.
Closing credits: The characters and events depicted in this photoplay are fictional. Any similarity to actual persons, living or dead, is purely coincidental.