The title refers to the penny dreadfuls, a type of 19th-century British fiction publication with lurid and sensational subject matter. The series draws upon many public domain characters from 19th-century British and Irish Gothic fiction, including Dorian Gray, Mina Harker, Abraham Van Helsing, Dr. Seward, Renfield, and Count Dracula from Bram Stoker’s Dracula; Victor Frankenstein and his monster from Mary Shelley’s Frankenstein; and Dr. Henry Jekyll.