Jane Asher asked Roger Corman if a friend could visit the set and join them for lunch. She explained that her friend was a musician who was about to do his first gig in London that night. At the end of lunch, Corman wished him good luck with his concert. Roger Corman had never heard of Paul McCartney until he read of the concert's success in the next day's newspapers.
Hop-Toad and Esmeralda were drawn from Edgar Allan Poe's short story "Hop-Frog." That story was inspired by an actual incident in 1393, where French King Charles VI and 5 of his lords dressed and chained themselves as "wild men" at a masquerade, and their costumes caught fire from a stray spark. Four of the lords died and the incident became known as the Bal des Ardents (Ball of the Burning Men).
The last words spoken in this film (by the Red Death character) are "sic transit gloria mundi" which translates into English as "thus goes the glory of the world."
Roger Corman had originally wanted this to be his second "Poe" picture following the success of "House of Usher (1960)." He passed it over because he felt that certain plot elements were too close to Ingmar Bergman's recent "The Seventh Seal (1957)."
Roger Corman and Daniel Haller were able to make this film look more opulent than earlier productions by using the sets left from "Becket (1964)." The two movies also share one actor: David Weston, who plays Gino here, played Brother John in "Becket."