Trivia: Fred MacMurray wears his real-life wedding ring throughout the movie. His character in the movie is single.
Trivia: The character of Jonathan is referred to several times in the film as a thug who "looks like Boris Karloff." This was an in-joke referring to the fact that Karloff played the role of Jonathan in the original Broadway production of Arsenic and Old Lace..
Trivia: Gaslight was teenage Angela Lansbury's first film and first Academy Award nomination and Ingrid Bergman's first Academy Award win.