When the professor is unconscious on the floor, Tilney (Rex Ingram) asks Sam if he is a doctor. Ironically, Rex Ingram was himself a trained physician in real life.
Cary Grant and Ronald Colman were both paid at least $100,000 for their work in the film. Jean Arthur, who was in Harry Cohn's doghouse and just coming off suspension, was only paid $50,000.
Nora tells the professor that he is, "as whiskered as the Smith Brothers." This refers to a brand of cough drops with an illustration of the Smith Brothers on the front, both of whom have a beard. First introduced in 1852, they remained the most popular brand for a century.