The language used in season two (Verbis Diabolo) is a fictional amalgam of Aramaic, Ancient Greek, Latin, and an obscure Arabic dialect called (in phonetic English) "Kan Allah Musali-Algins". The language, Verbis Diabolo was created specifically for the show by the curator of the London Historical Societies Emeritus Professor of ancient languages.
As Creator John Logan had never written a television series before, he did not produce a speculative script, but instead wrote the first two episodes directly. When he had the opportunity to pitch it to Showtime, he also wrote a forty-page "bible" exploring the characters and story, with the network eventually buying the show.
Penny Dreadful is an old term used during the nineteenth century to refer to cheap popular serial literature, and it could be interchangeable with penny blood, penny awful, or penny horrible. It means a story published in weekly parts, with the cost of one (old) penny. The main plot of these stories were typically sensational, focusing on the adventures of detectives, criminals, or supernatural entities.
The séance back-bending scene was filmed in three different segments: the first was on set with Eva Green standing on the table; the second was filmed in a studio where the actress bent her body as far back as the stuntmen deemed safe; the third was Eva bent all the way back in a contraption, the last was filmed in front of a greenscreen. The post-production team then combined all three segments into one.
In this show, Dr. Victor Frankenstein likes to quote the romantic poet Percy Bysshe Shelley. Shelley's second wife, Mary Wollstonecraft Godwin Shelley, was the author of the 1818 gothic novel Frankenstein; or, The Modern Prometheus, from which the characters of Dr. Victor Frankenstein and "Frankenstein's monster" originated.
The show used many metaphors to point out the hidden or dual nature of the main characters. One of them is shooting scenes in reflective surfaces like mirrors. Most notably though, is the dark versus light depiction of Vanessa and Mina.
Sarah Greene stated in an interview, that the make-up for Hecate and the other witches' Nightcomer forms consists of several different pieces, which take several hours to apply. She stated that the breasts and genital regions are fake, and are part of the prosthetic. However, Greene forgot the instructions not to drink alcohol before putting on the make-up, as sweating alcohol would negate the adhesive used. Once while shooting in the make-up, her chest-piece fell off.
Simon Russell Beale based his accent for his character, Ferdinand Lyle, on the accent of the renowned playwright Tom Stoppard. Stoppard was born in Czechoslovakia, but while still a young boy, his family fled the Nazis. They went first to India (where he spent three years), where his Czech mother was remarried to a British Army Major, and subsequently Tom was educated in north-central and northeast England. Consequently, Stoppard's adult accent, though mostly standard Received Pronunciation English, is a unique combination of many diverse linguistic and dialectical influences.
The shows boasts four cast members, who appeared in several James Bond films. Timothy Dalton played the title character in The Living Daylights (1987) and Licence to Kill (1989). Eva Green played Bond girl Vesper Lynd in Casino Royale (2006). Helen McCrory played Clair Dowar MP in Skyfall (2012). Rory Kinnear played Tanner in Quantum of Solace (2008), Skyfall (2012), and Spectre (2015). In addition, Writer and Creator John Logan co-wrote the screenplays for Skyfall (2012) and Spectre (2015), and Executive Producer Sam Mendes directed the latter two films.
Frankenstein's monster sometimes uses the names "Caliban" or "John Clare". Caliban, the name first given to him by the actor Vincent Brand, is a character from Shakespeare's play The Tempest who (like the monster) is described both as monstrous ("A freckled whelp hag-born--not honour'd with / A human shape") and sensitive, with a legitimate grievance against his master Prospero. John Clare was a real English poet during the Romantic movement (the same era as more famous writers such as Lord Byron, John Keats, Percy Shelley, and Shelley's wife and "Frankenstein: or, The Modern Prometheus" author Mary). Clare had a tragic life; although his mostly rural-themed poems were generally well-received, their sales were not sufficient to earn him a living to support his wife and children, especially after he started suffering from mental illnesses and alcoholism. He was institutionalized due to his florid delusions, which included the beliefs that he was really Shakespeare or Lord Byron in disguise; that he had multiple wives; and that he was a celebrated boxer. The Shelleys and the real Lord Byron knew each other well, and it was while they were all on vacation together in Switzerland, that Mary Shelley first conceived the Frankenstein story.
Hecate Poole, the witch who pursues Ethan Chandler in seasons two and three, shares her name with the ancient Greek goddess of witchcraft and the moon. This link to the goddess Hecate fits the character perfectly, as it reflects her status as a Nightcomer witch, and her infatuation with Ethan, the "Wolf of God", who transforms into a wolf when the moon is full.
The Grand Guignol (in London as depicted in the show) is not a real theatre. It was constructed for the filming of the series. It was a real theater in Paris in the late nineteenth and early twentieth centuries. The style of plays common in this theater eventually ended with that style of storytelling being call "Grand Guignol".
When the director scheduled to direct the finale of season three had to back down, the producers and the cast (specially Eva Green) demanded Paco Cabezas to be back, after having helmed episodes five and six of the same season, because they had a great working experience.
The manner in which Vanessa sizes up and breaks down Ethan Chandler during their first meeting is remarkably similar to the way Vesper Lynd, a previous character of Eva Green's, does to James Bond in Casino Royale (2006).
Similarities to the original Dracula novel: Dracula acts more as a permeating force throughout the series, than actually being a physical threat. The same goes for about three quarters of the book. Dr. Seward uses a phonograph, which was a novelty when the original book was published. "Children of the night, what music they make" is a reference to the original Dracula (1930) starring Béla Lugosi, as the Count says "what sweet music they make" in the book. The characters Dracula, Professor Van Helsing, Mina Harker (née Murray), Dr. Seward, and Renfield all have a role in Penny Dreadful. Jonathan Harker is only mentioned. Major differences and liberties taken from the original book: Dr. Seward is American in this show. The only American in the original, was a Texas man called "Quincey Morris". Renfield is Dr. Seward's secretary in the series. In the book, he's an assistent to a real estate agent that gets touched by the evil of Dracula and goes insane in the process, leaving him with a constant lust for the blood of small living creatures. Rather than fully fledged vampires, the Dracula of the series seems to be more reliant on an army of vampiric minions, similar to Renfield. In the first season, the party of heroes is attacked by more "traditional" fang sporting vampires. In the book, there are only five vampires: Dracula, his three brides, and Lucy Westenra. While Mina Harker is portrayed as a vampire in multiple films and series, including this show and The League of Extraordinary Gentlemen (2004), she's never fully turned into a vampire in the novel. Professor Van Helsing only plays a small role in this show. In the book, he leads the "pack of hounds after the fox", as the human protagonists travel far and wide in pursuit of The Count.
In the season three opener, when Vanessa visits the museum, the two animals that she views closely are a wolf and a case of scorpions. These are the two animals that represent Ethan and Vanessa respectively.
Patti LuPone previously played another character named Joan on American Horror Story (2011). She played an over-zealous fundamentalist Christian named Joan Ramsey who lived next door to Miss Robichaux's Academy for Talented Young Ladies, a witches coven. Ironically, LuPone would later go on to play the Daywalker witch Joan Clayton on this show.
The trivia items below may give away important plot points.
John Logan wrote the role of Evelyn Poole, a.k.a. Madame Kali, specifically for Helen McCrory, and told her from the beginning the truth about the character and how her importance would arrive in the second season.
Vanessa Ives is shown to be writing a constant stream of letters to Mina Harker (one of the protagonists of Bram Stoker's Dracula). Stoker's book was written in epistolary format, a series of letters, diary entries, and ship's log entries.
Eva Green asked for her last scene to shoot not to be Vanessa's death but something else, because she didn't want to play the character for the last time in those circumstances, so the last scene she shot was the one where Vanessa is in her bedroom looking at the space where the cross used to be.
Ethan Chandler's (Josh Hartnett's) real name is revealed to be Ethan Lawrence Talbot. This is a reference to the character Lawrence Talbot, portrayed by Lon Chaney, Jr. in The Wolf Man (1941), and its subsequent series of sequels, and Benicio Del Toro in its remake, The Wolfman (2010). Contrary to what has since become a custom in werewolf films, the 1941 original never shows a shot of the full moon. This does, however, appear in this show during Ethan's transformation scenes.