Random Trivia For This Title:
- Cameo by Brian Greene: The film's physics consultant appears early in the movie as himself, being interviewed by Dick Cavett. There are two scenes; one with old footage of Dick Cavett interviewing Brian Greene in 1969, then a scene with an interview in 1999 with contemporary footage of Dick Cavett and an "aged" Brian Greene.
- Elizabeth Mitchell broke her nose during production.
- In 1997 Renny Harlin was going to direct the film with Sylvester Stallone playing the lead, but Stallone asked too big paycheck and eventually neither Stallone or Harlin was involved in making the picture.
- Referenced in [Reno 911!] episode where an aspiring novelist's apartment is burning he asks the Sheriff's and Firefighters to save his only copy. They find out it is basically the same story as Frequency and give the novelist the bad news.
- All of the World Series facts were true in this film. The Mets [?] Cleon Jones really did get hit on the shoe with a pitched ball. At first the umpire didn't award him first base but when Mets Manager [?] Gil Hodges showed him the shoe polish on the ball the umpire changed his call and awarded him first base. It became known as the "Shoe Polish Incident".
- W2QYV, Frank Sullivan's Ham Radio call-sign, actually belongs to the Niagara Radio Club in Lewiston, NY
- In the warehouse fire scene, all the firefighters except Dennis Quaid, Peter MacNeill and Jordan Bridges, are real.
- Elizabeth Mitchell plays Jim Caviezel's mother. In reality, Mitchell is younger than Caviezel. Similarly, though the story and Mitchell's portrayal suggest that her character is about the same age as her husband, played by Dennis Quaid, she is 16 years younger than Quaid. At the time of the film's release, Quaid had just turned 46, Caviezel was 31, and Mitchell was 30.
- Dennis Quaid received 16 stitches just above his hairline after being injured in the stunt where he slides down the construction funnels during the warehouse fire.
- On April 25, 2000, the New York Mets and Cincinnati Reds played a game wearing their 1969 uniforms to promote the film.
- Director Gregory Hoblit was a co-executive producer of [Hill Street Blues]. He directed the episode seen in the film that's on TV as John is calling his mother.