Following the film's massive box-office success, Warner Bros. planned to give Mel Gibson, producer Joel Silver, and director Richard Donner brand-new black Range Rovers as thank-you presents. However, Warner Bros. chairmen Bob Daly and Terry Semel only told Donner that they were invited to a celebratory lunch (the Range Rovers were going to be a surprise gift) and Donner wanted to invite Danny Glover, Joe Pesci, Rene Russo, and screenwriter Jeffrey Boam to join them. So the studio simply raced around Los Angeles, and kept buying one new Range Rover for each new lunch guest, and presented them to the entire happily stunned group when the meal was over.
Murtaugh's boat is called "Code 7", which is the L.A.P.D code for a lunch break.
During the scene where Riggs and Lorna are comparing scars, many of Riggs' were given to him during the events of Lethal Weapon 2 (1989), specifically the gun shots in his lung and the knife wound in the back of his leg.
When Lorna Cole says to Riggs "Close is a lingerie shop without a front window," Riggs doesn't know how to react to the comment. This was an ad-lib by actress Rene Russo. So not only does the character not get it, actor Mel Gibson doesn't either.
Bill Frederick: The Mayor of Orlando, Florida, is the policeman who says "Bravo" to Murtaugh and Riggs after the explosion of the building in the opening scene, which was the old Orlando City Hall.