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 portrayed "Junior" in the later Hart to Hart movies.
The Harts' dog, Freeway, was so named because he was found by the side of a freeway.
The Harts' ranch-style house originally belonged to Dick Powell, an old friend of Robert Wagner, and was situated in Mandeville Canyon, Los Angeles, California.
The last "Hart to Hart" movie aired on Aug 25, 1996, exactly seventeen years, to the date, of the airing of the pilot.
The last name of Max (Lionel Stander) was never mentioned throughout the show.