The character of Vulcan (played by Corbin Bernsen) was not in the source novel; he is a new addition to the TV adaptation. The character is based on the ancient Roman god of fire, the forge, and metalworking, but the inspiration for the new character did not come directly from ancient mythology. Instead, the idea came from a story that Neil Gaiman told showrunners Bryan Fuller and Michael Green about traveling through Birmingham, Alabama, and seeing the 56-foot-tall cast-iron statue of Vulcan that overlooks the city on Red Mountain. In an Entertainment Weekly interview, Green said that Gaiman was told that during Birmingham's heyday as a steel town, one steel mill had had a policy that it was cheaper for them to pay restitutional damages to the families of workers killed on the job rather than to pay to ensure their safety. The "torch" in Vulcan's hand would light up one of three colors to communicate the safety of the Mills - a green torch indicated that no employees had been injured during the previous 24 hours, a white torch indicated minor injuries and a red torch signaled there had been a fatality in the previous 24 hours. Green said that Gaiman characterized that policy as "as modern a definition of sacrifice as there might be".
Season 1 originally had 10 episodes, but after seeing the cuts for episodes 3 and 4, the producers decided to merge them into one single episode and then use the cliffhanger for the second to last episode as the season finale, then using parts of the original season finale through the whole season. Hence making the season 8 episodes long.
The whole Laura backstory wasn't in the book, it was created by the creators of the show to develop more the lead female character. In fact, Emily Browning was directly presented with the script for the Laura centered episode when offered the role.
Bryan Fuller asked Gillian Anderson to play Media while she was performing "A Streetcar Named Desire" in Brooklyn, NY and came to her last performance. Two days after the show closed, Gillian flew to Toronto to start filming.
Neil Gaiman declared in twitter in May 2016: 'Just saw @GillianA in A Streetcar Named Desire at St Ann's warehouse. She was remarkable, powerful, funny, tragic. shar.es/1eBJbq'. The day after Gillian Anderson finished the play, flew to Toronto in order to appear in the series as Media.
There are many nuances in this storyline for the first season. The neon lights in the posterior title of the series, all the cats, and a number 55 on his motel door. All of these are underlined with death.
Actor Orlando Jones received a consulting producer on the second season because, according to The Hollywood Reporter, "after some actors, including star Ian McShane (Mr. Wednesday), began taking passes at improving dialogue, the production was forced to enlist Jones as a writer on the series so a member of the WGA would be credited with writing instead of having actors violating guild rules".
Emily Browning's character Laura Moon is the wife of Shadow Moon (Ricky Whittle), who after she dies, is referred to by Mad Sweeney (Pablo Schreiber) as "Dead Wife". Emily Browning's character Frances Shea in "Legend" (2015), is married to Reggie Kray (Tom Hardy) and eventually commits suicide, but is the film's narrator - a "dead" wife.
The trivia items below may give away important plot points.
Odin (Woden, Wotan), portrayed by Ian McShane, goes by the name Mr. Wednesday. "Wednesday" is derived from the Old English "Wodenstaeg", "day of Woden". Or as in the Scandinavian languages (NO DK SE) Wednesday is still called Onsdag shortened from Odensdag, which comes from the old norse word óðinsdagr - Odin's day.
When they show the map of Wednesday and Shadow's road trip to Vulcan, VA, they pass very close to Floyd, VA. Floyd is the location of the real-life inspiration for the tree from the novel. Its specific location is kept private out of respect for the property owners.