In order to keep costs down, the film's producers did not want to pay royalty fees for the use of the names "King Kong", "the Frankenstein Monster", "the Bride of Frankenstein", "Quasimodo" and "the Creature from the Black Lagoon". That is why many of the characters - though recognizable - are all called by different names; i.e., King Kong is "IT", the Frankenstein Monster is "Fang", the Bride of Frankenstein is simply "the Monster's Mate", Quasimodo is called "the Hunchback of Notre Dame" and the Creature from the Black Lagoon is called simply "the Creature". The names "Count Dracula", "Dr. Jekyll and Mr. Hyde", and "the Invisible Man" were in the public domain at the time of the film's production and thus, as no royalty fees were required for their use, they were used in the film.
Among the many talented people who worked on this film are several who did not work in films very much. One example is noted cartoonist Jack Davis - best known for his work on Mad Magazine (of which he was a co-founder). Mr. Davis was the characters' designer. Noted for his characters with distorted anatomy, his outre style gave Francesca her (quite) ample bosom (which was not typical in "kiddie entertainment").
With the exception of Baron Boris von Frankenstein, Allen Swift voiced every other male character in this film. Despite this film being a musical and Allen Swift voicing a majority of the characters, none of his characters ever sing.
The dialogue at the film's very ending is a parody of the final scene of the film Certains l'aiment chaud (1959).
In September 1967, Dell Publishers released the comic book adaptation of this film. Priced at 12 cents, it was 36 pages long, made in color, and featured three stills from the film on the cover.