Son of Frankenstein

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 Wyllis Cooper screenplay. Lugosi 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, Sara Karloff was born on his 51st birthday, November 23, 1938.

Horror legend Christopher Lee rated "Son of Frankenstein" as one of the best horror films.

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 to 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 (1995) and 100 Years of Horror (1996), courtesy of Sara Karloff.

Because of the decline in Bela Lugosi's career, he was originally cast for a very low fee. Rowland V. Lee felt that Lugosi was being taken advantage of, so he fattened up his part by writing more dialogue for Ygor, so that Bela be paid a more appropriate fee. Karloff had absolutely nothing at all to do with this, contrary to what urban legend was made up by Karloff's fans turned biographers.

Makeup artist Jack P. Pierce estimated it took four hours to transform Boris Karloff into the monster.