Mel Gibson references the Three Stooges several times in the film. In real life, Gibson is a big Stooges fan, and in 2000, he produced the biographical TV movie "The Three Stooges."

The helicopter from which Hunsacker is shot by Mister Joshua is FAA registry number N230CA, meaning it's the same Bell JetRanger wearing a POLICE paint scheme that is shot down in the movie 'Blue Thunder' (1:21:30).

After having visited Murtaugh's house and family for the first time, Riggs tells him outside a story from Vietnam, how he "shot a man from 1000 yards in the windy weather" and adds: "That's the only thing I ever been good at." Talk about understatement. Of course he's nothing else but martial arts expert, ladykiller, wisecracking innocent people's life saviour and bad boys' biggest nightmare who can make it through almost impossible situations.

During the scene in which we see Murtaugh talking to Hunsaker about his involvement with the Drug dealers. Hunsaker mentions 'Air America', a CIA front during the Vietnam. Air America was a film regarding this very thing staring Mel Gibson and filmed three years after Lethal Weapon.

In the scene where Danny Glover and Mel Gibson are intervewing the kids who also saw the hookers house blow up, one of the kids has an orange hat on with a black "B" on it. That is the hat for the younger age groups of a summer baseball league in NYC called the "Bonnies." I know this for a fact because I played for the organization my whole life. Why would a kid in LA be wearing the hat? Only interesting to people from NYC, I guess.