Arsenic and Old Lace/Trivia
- Actor Allusion:
- The Boris Karloff Casting Gag below (which was only for the original run of the play).
- For the movie, Cary Grant leans against a tombstone with the name "Archibald Leach".
- The casting of Peter Lorre as a crazed German surgeon may be a callback to Mad Love.
- Hey, It's That Voice!: You might not recognize Mr. Witherspoon's face, but you've probably heard Edward Everett Horton narrating "Fractured Fairy Tales" on Rocky and Bullwinkle.
- Money, Dear Boy: Inverted-- Cary Grant was so dissatisfied with his performance in this movie that he donated his entire salary from it to charity rather than profit from it at all.
- Playing Against Type: Cary Grant, who usually plays suave and sophisticated characters, in the movie plays a character who starts out like that, but becomes increasingly panicked and flustered as the story goes on.