Although Clint Eastwood made the phrase "Go ahead, make my day" famous, it was originally used a year earlier by actor Gary Swanson in the movie Vice Squad. Swanson, who played a Hollywood vice cop, said the line, "Go ahead scumbag, make my day," to actor Wings Hauser, who played a pimp, during a bust.
The scene where Callahan chases the robber in the senior citizen bus was filmed at and around the Pacific Garden Mall in Santa Cruz, California. This area was heavily damaged in the Loma Prieta earthquake on 17 October 1989. Many of the buildings in this scene had to be razed, due to extensive earthquake damage.
The reason the film was made at all had to do with a survey. Warner Bros. was preparing to release the Sean Connery James Bond film Never Say Never Again and they took a survey. They asked movie goers to name an actor and a famous part that actor played. Clint Eastwood as "Dirty Harry" scored so high in the survey results, the studio told Eastwood it would be "open" to distributing another "Dirty Harry" film. Eastwood made this film as a result of that meeting.
The carousel Jennifer is researching is the "1911 Looff Carousel" located at the Santa Cruz Beach Boardwalk in Santa Cruz,California. In 1987 the U.S. Park Service declared the ornate merry-go-round a National Historic Landmark along with the Boardwalk's 1924 Giant Dipper roller coaster.
Clint Eastwood and Pat Hingle previously appeared together in Hang 'Em High. Coincidentally, both films feature Eastwood as a tough guy lawman who borderlines on vigilantism and Hingle as his superior who has a heavy disdain for the way he does things.
The movie's most famous quote, "Go ahead, make my day..." is often erroneously attributed by most people to be a quote from the first movie of the series, Dirty Harry.
The indelible catchphrase "Go ahead, make my day" went on to be further immortalized when then US President Ronald Reagan used it in a key address: "I have only one thing to say to the tax increasers: Go ahead, make my day." (March 13, 1985, in a speech threatening to veto legislation raising taxes).
The air traffic controller who speaks to Lt. Briggs wears a pocket protector which reads "PATCO". This stands for "Professional Air Traffic Controllers Organization" and was the union whose members were fired by 'Ronald Reagan' for going on strike in 1981.
The only 'Dirty Harry' film to make reference to Eastwood's Man With No Name trilogy. The specific scene is when Harry is cornered on the dock and gets his left hand squashed, as does it happens in _A Fistful Of Dollars (1964)_ and then returns as the avenger using the gun in his right hand.
The trivia items below may give away important plot points.
The production company had to keep a diver on the set during the filming of the climactic scene filmed on a pier in which Callahan shoots the bad guy. When the gun would jam, which it did frequently, Eastwood would in a fit of rage throw the gun a considerable distance into the water. The diver would retrieve the gun, which would be dried out, repaired, and reloaded for the next take.