Bela Lugosi's performance in this film is considered by many to be his greatest.
Boris Karloff became a father for the first time while filming this movie.
As part of an article about this movie in a 1967 issue of his magazine "Famous Monsters of Filmland," Forrest J Ackerman published two stills of Boris Karloff as the Monster and Edgar Norton as Benson the butler. In the first, the Monster is standing just behind the other, who is holding a tray bearing a plate of chicken. In the other, the Monster is eating a chicken leg while Benson lies in a heap before him. As no such sequence appears in the movie, from these Ackerman postulated that a scene of the Monster killing the butler had been filmed but left on the proverbial cutting room floor.
At 99 minutes this was the longest English-language film in the classic Universal horror series (the Spanish version of Dracula Drácula was about five minutes longer). Most of the films had running times of less than 80 minutes, which served to increase the number of showings possible in theaters.
Both Claude Rains and Peter Lorre reportedly were considered for the role of Wolf von Frankenstein; Lorre's casting was publicly announced.
Despite his frequent appearances in horror films, Basil Rathbone had a particular disdain for them. This is likely the reason for his 'over the top' performance. (Source: 'Universal Studios Monsters: A Legacy of Horror' by Michael Mallory")
Due to the lack of a prepared script, much of the picture was written just moments before the actors were to shoot their scenes. This was how director Rowland V. Lee was able to keep Bela Lugosi working throughout filming, and built up the role of Ygor, which never appeared in the original Willis Cooper screenplay. The actor was forever grateful to Lee for allowing him to create what turned out to be one of his very best characterizations. After many delays, shooting finally started November 9, 1938, finishing January 5, 1939, just days before its prescribed release date of January 13. Boris Karloff's daughter was born on his 51st birthday, November 23, 1938.
Makeup artist Jack P. Pierce estimated it took four hours to transform Boris Karloff into the monster.
Part of the original SHOCK THEATER package of 52 Universal titles released to television in 1957, followed a year later with SON OF SHOCK, which added 21 more features.
Plans were discussed to shoot the film in Technicolor, but the decision was made to revert to black and white; both director Lee and co-star Josephine Hutchinson verified in later years that the film was designed for, and shot in monochrome. Urban myth has it that Karloff's make-up photographed bright green and was a primary reason for shooting in black and white. An urban myth has it that Dwight Frye was in the Technicolor test reel and was subsequently dropped from the cast. In the late 1980s a reel of Technicolor test footage was discovered in Universal's vaults, but was either stolen from the desk of the executive who was in possession of it (according to one story) or simply boxed back up by bureaucrats and shipped to a New Jersey film vault (according the film archivist who actually found the reel.)Karloff family home movies shot on the set of the film reveal the Monster's coloration to be grayish with subtle highlights and shadows of blue-green and brick red. The brief clips show Karloff in Monster make-up sticking his tongue out at the camera and pretending to strangle make-up artist Jack P. Pierce can be seen on the CD-ROM The Interactive History of Frankenstein and
The character of Ygor (played by Bela Lugosi in the final film version) does not appear in Wyllis Cooper's October 20, 1938, draft of the screenplay titled "The Son Of Frankenstein". Director Rowland V. Lee was annoyed at Universal's low-balling of Bela Lugosi (who was being paid only $500 per week because he desperately needed a job and Universal knew it), and he kept rewriting the script to make Lugosi's character more central, and to make sure that Lugosi ended up with a decently sized paycheck. The "Ygor" character died in the film, but returned in the sequel, The Ghost of Frankenstein; for unknown reasons, the spelling of the name was altered to "Igor" in the credits (yet the script for the even later Frankenstein Meets the Wolf Man reverted to the original spelling "Ygor."
The name of the town where the action takes place is "Goldstadt" in the first two films in the series, Frankenstein and Bride of Frankenstein. Here it is called "Frankenstein." In the two subsequent films, the stories would take place in another fictional town, "Vasaria" (or "Visaria").
This film marks the final time Boris Karloff would play the "Monster" - at least in a feature film. In August of 1940 he appeared as the Monster in a celebrity baseball game, with Jack P. Pierce in attendance (Pierce was a coach for an amateur baseball team, and played semi-pro when he was younger). In the next Frankenstein film in which Karloff appeared, House of Frankenstein, he played Dr. Gustav Niemann. Originally the Samuel Goldwyn film The Secret Life of Walter Mitty was to have had a fantasy sequence in which Mitty (Danny Kaye) confronted the Monster, played again by Karloff (who played the villain in "Mitty.") Goldwyn sought and received authorization from Universal to use the image of the Monster, and Pierce re-created the make-up. Stills exist of the film's director, Karloff, Pierce, and Evelyn Karloff, but it has not been verified that scenes were actually filmed. In the Allied Artists film Frankenstein - 1970 Boris was an elderly Baron Frankenstein - but the twist ending was the revelation that the Baron had recreated the Monster's face