The scene between Tom Hanks and Victor Garber crying over the movie The Dirty Dozen (1967) was completely improvised during the take.
While making the film, Nora Ephron was focused on its long-term legacy: "Our dream was to make a movie about how movies screw up your brain about love, and then if we did a good job, we would become one of the movies that would screw up people's brains about love forever."
Despite playing the role of his sister in the movie, Rita Wilson is the real-life wife of Tom Hanks. They had been married for five years at the time of the release of this movie.
Nora Ephron: When Meg Ryan's character is in the kitchen in the middle of the night listening to the 'best of' radio callers, the caller 'Disappointed in Denver' is voiced by Ephron.