A pre-Seinfeld (1989) reference to the real-life "Soup Nazi": A male journalist is speaking as Meg Ryan enters an office at her newspaper, saying, "...he's the meanest guy in the world, but he makes the best soup you've ever eaten."
In "Everything Is Copy," the 2015 documentary about Nora Ephon's life and career, Tom Hanks reveals that there was another child actor cast as his character's son, Jonah, before Ross Malinger, but Ephron thought the first kid was not working out and she fired him. Hanks avoided specifying who that first child actor was.
When Jonah says that when you reverse the record, it says "Paul Is Dead". This is a reference in 1966 that a rumor said that The Beatles' Paul McCartney died in a car crash and was replaced by a winner of a "Paul McCartney Look-alike Contest". The rumor also said that if you reverse some of their songs, it will send messages that Paul is dead.
David Hyde Pierce expresses psychological opinions to Meg Ryan about relationships, and in the course of discussion, remarks about Seattle's rainy weather. David is later cast as Frasier Crane's psychiatrist brother, living in Seattle, in Frasier (1993).
In Spain this movie's title wasn't "Sleepless In Seattle" translated into Spanish, as one would expect. In the past, the titles of movies weren't literally translated. This was the case with the film "An Affair To Remember", the movie with Cary Grant and Deborah Kerr, referred to in this film. That film was named "Tú y yo", which was the Spanish translation of 'You and me'. So, when they re-named "Sleepless in Seattle" they used the translation of the original name of the Cary Grant film, naming it "Algo para recordar".
Legendary American arranger Gordon Jenkins appears a couple of times in the movie's soundtrack: "As Time Goes By", sung by Jimmy Durante, is the Jenkins arrangement. The version of "Stardust", sung by Nat King Cole, is the Gordon Jenkins version.
The ring, which belonged to Walter's mother, that he had sized down for Annie, is in fact a Tiffany & Company ring. Although it isn't being made anymore, there is a very similar one available- "Flower ring" for 4,900 dollars on Tiffany.com.
In addition to on-location shooting, many interior "house scenes" were filmed in Seattle, including scenes that took place in Baltimore and New York City. Sets for the movie were constructed in old hangars at Sand Point Naval Air Station, a decommissioned naval base in north Seattle. The final meeting between Sam and Annie was filmed on a Seattle set that had been made up to look like the observation deck of the Empire State Building.