In the movie Jack Nicholson plays a notorious bachelor, who always: "escaped the noose", while Diane Keaton plays a divorcée. In real life it's the other way round. Jack Nicholson is divorced while Diane Keaton never married.
First (albeit brief) full frontal nudity scene for Diane Keaton. Although highly publicized as her first actual nude scene, in fact, she first appeared topless 26 years earlier in Looking for Mr. Goodbar (1977).
The American poster for this film featured large pictures of Jack Nicholson and Diane Keaton. In Japan, the poster also included a large picture of Keanu Reeves, presumably because of his popularity there at the time.
DVD includes a deleted scene where Harry sings "La Vie En Rose" for Erica in a karaoke bar. Part of this scene (Harry and Erica dancing) was in one of the trailers. Jack Nicholson sings the same song during the end credits.
When Erica kisses Harry in the scenes outside the restaurant in New York City, it was an improvisation by Diane Keaton. Writer/Director Nancy Meyers liked it so much that she decided to use it in the final cut of the movie.