The dog who portrayed Freeway, was found in an animal shelter and was named "Charlie Gray". On the set, he was especially close to Stefanie Powers. His offspring would portray "Junior" in the later Hart movies.
In season four, episode nineteen, "A Change of Hart", the Hart address is listed as 3100 Willow Pond Dr. Bel Air, California, 29042. However, that ZIP code is actually located in Denmark, South Carolina. In season five, episode twenty-one, "Always, Elizabeth", the Hart's address is listed as 3100 Willow Pond Dr. Beverly Hills, California, 90047.
On November 29 1981, when Hart to Hart was still on the air, Natalie Wood, husband Robert Wagner and friend Christopher Walken took a late night boat ride, during which Wood drowned in the Pacific Ocean. The death was originally ruled an accident, but now the investigation has been re-opened.
Sidney Sheldon had originally written a script for CBS called "Double Twist", about a married couple who were also both spies. Aaron Spelling and Leonard Goldberg decided to update the idea for a potential television series. They asked Tom Mankiewicz to update the script, to make it more contemporary, and viable for a potential weekly series. Mankiewicz re-worked Sheldon's original script, and it was renamed "Hart To Hart". Mankiewicz also made his directorial debut with the pilot episode as planned, and remained a "Creative Consultant" on the series.