During production, Richard Donner was shocked when Mel Gibson confided that he was drinking five pints of beer for breakfast. Despite his alcohol problems, Gibson was known for his professionalism and punctuality.

Jack McGee ad-libbed his line about the condom commercial during rehearsals. The cast and crew liked it so much, it was kept in the film.

Leo's "okay-okay-okay" schtick was based on Disneyland employees giving directions to guests at Fantasyland. Originally, Leo was going to be an oily, effeminate character, but Joe Pesci didn't want to play him that way. He pitched the idea of making Leo all-too-eager to please, complete with "okay-okay-okay" ad libs, to Richard Donner. Donner laughed and said, "Do that! Do that!" The phrase is referred to in Home Alone (1990) by having the phrase "Oh, K Plumbing" painted on a van driven by Joe Pesci's character.

The scene where Mel Gibson attaches cables to the stilts of a mountain-top house, and pulls it down, cost over five hundred thousand dollars.

After the first movie turned out to be huge hit, earning one hundred twenty million dollars worldwide on a budget of fifteen million dollars, it was decided to make the sequel. Producer Joel Silver asked writer of the first film Shane Black to write the script for the sequel, and Black agreed. Despite having some problems in his personal life, Black managed to write his first draft of the script in six months, along with his friend, novelist Warren Murphy, co-creator of Remo Williams (the lead character of The Destroyer novels) which itself was turned into Remo Williams: The Adventure Begins (1985). Although many people thought that their script was brilliant, Warner Brothers and producers, including Silver, and director Richard Donner, however, disagreed with Black's decision to kill off Riggs' character in the ending, because they wanted to keep him alive for future sequels, and they also thought that Black and Murphy's script was way too bloody and dark, and they wanted a lighter, more comedic script, while their draft was completely serious, and it focused more on courage and heroics, like Riggs coming full circle, from the way he was in the first film, and how his relationship with Murtaugh and his family brought him back to life, and into the real world, helping him to let his guard down, and learn to accept the love of real people, and in Black's version of the script, it's the very love that makes Riggs willing to die to protect them. Other parts from Black and Murphy's script, which were changed or left out of the final version of the script, include Leo Getz being only a minor character, and having only one scene, and few lines of dialogue. A lot more violence throughout, like South African villains, who were even more vicious in the original script than in the final film, torturing Shapiro, a female police officer working with Riggs and Murtaugh (the one who is killed by a bomb in the pool in the film) to death in a very nasty scene. There was also a scene where Riggs is tortured by South Africans in a similar way like he was in the first film, but much worse. The script also included an action sequence, in which plane full of cocaine gets destroyed, causing for cocaine to fall all over Los Angeles like snow. The ending of the script included a climactic battle, which took place on hills engulfed with a big brush fire, and after the destruction of the stilt house, Riggs chases Benedict (original name of the villain Pieter Vorstedt from the movie) who was different, and lot more dangerous in the original script, and Riggs' "arch-nemesis, his worst nightmare" as Black himself said, into the fire. After the final battle with Benedict, Riggs dies very slowly after he gets stabbed by him. The last scene in Black's script, was Murtaugh watching the video tape that Riggs made earlier, since he had a premonition that he was going to die, and in which he says his goodbye to Murtaugh. Following the studio's negative reaction on his script, and their demands for massive re-writes, Shane Black left the project after six months, earning only one hundred twenty-five thousand dollars for his work (Warren Murphy also earned the same amount), and never worked on any of the other sequels. Black said in later years in interviews how he considers his original script for Lethal Weapon 2, which was also called "Play Dirty", to be his best work, and most intense script he has written, and how other than the scene where stilt house gets destroyed, his script was completely different than the one used for filming. He also said how the problem with the final version of the second movie was that they did too much comedy, and how he dislikes the other two sequels of the film, because of the way they ruined Riggs' character. Despite many attempts by fans of the Lethal Weapon movies, and Shane Black, his original script for the second film was never found, and it remains a highly demanded, and the most wanted, of all of Black's scripts.

During the scene where Martin Riggs is talking about his gold pen, and is making what is presumably a pot of chili, he can be seen crushing Oreo cookies into the pot. Later in the movie, Riggs asks Rika if she likes her chili "with or without crushed Oreos".

The "bomb in the toilet" sequence was used as an early teaser trailer for the movie. The trailer ended with the toilet landing on Murtaugh's car and the voice-over announcer saying "They're not taking any more crap!"

The scene where Murtaugh does his "Free South Africa" tirade - his statement of "One man, one vote" did, in fact, became part of then-South Africa's President F.W. de Klerk's agenda to end Apartheid, lift the ban on the African National Congress (in the film, protesters outside the South African Consulate had the ANC flag), and released Nelson Mandela from incarceration. Danny Glover portrayed Nelson Mandela in the made-for-cable HBO film Mandela (1987), which was filmed prior to the release of the first Lethal Weapon film.

Despite the film's anti-South African stance, it was passed uncut by the South African censors, and became a major financial success in that country.

Patsy Kensit described her sex scene with Mel Gibson as having been very uncomfortable to act out. She stated that the reason was that she and Gibson were both married, and both Catholics.

According to Richard Donner's commentary for the film, although they rejected Shane Black's original draft of the script mostly because of the ending where Riggs dies, they still filmed the ending of the movie in a way that they could edit it in two different versions of it; Riggs dying, or Riggs surviving. After a good response from the audience during test screening of the movie, it was decided to keep Riggs alive. The last shot of the movie showing Riggs on the ground, and Murtaugh holding him while the camera moves away from the scene into the air, showing the sunrise, was actually meant to be used in the ending where Riggs dies, which is why both he and Murtaugh don't move during the shot, so in a way, the movie does end with Riggs dying from his wounds. Michael Kamen's track "Riggs Dying", and Eric Clapton's cover of the song "Knocking on Heaven's Door", were composed and meant to be used only in the "Riggs Dies" ending, so George Harrison's song Cheer Down was used for ending credits, once the "Riggs Lives" ending was chosen for the final version of the film.

On the side of Riggs' refrigerator is a U.S. Army Military Police School diploma.

One scene that was cut out, but restored in the DVD Director's Cut, is an extended version of Leo trying to show Riggs and Murtaugh where the "house with stilts" is located. In the scene, they are parked off road, and Leo is trying to recall the address. He keeps going on and on that the address has to add up to nine, because "nine is my lucky number". Meanwhile, Riggs and Murtaugh look through a map book, and randomly pick a street to go down. Following this scene is the one already in the film, of them finding the house. The deleted scene further explains Leo's remark "I told you. Nine. That's my lucky number," after Murtaugh moans "This is the ninth possibility, Leo."

The prop Beretta 92fs Mel Gibson uses in this film, is the same prop gun he would use in Lethal Weapon 3 (1992) and Lethal Weapon 4 (1998). Not only that, but this also the same prop gun Bruce Willis used in Die Hard (1988), Die Hard 2 (1990), and Die Hard with a Vengeance (1995). The prop is now a retired prop.

In the scene in which Leo is cleaning Martin Riggs' house, you can hear the song "I'm Not Scared", by the short-lived British pop group Eighth Wonder, of which Patsy Kensit was the lead singer.

Jeffrey Boam, who took over writing of the script for the film after Shane Black and Warren Murphy's script was rejected for being too dark and bloody, and because Riggs died at the end, also wrote the script for third Lethal Weapon film, and an unused draft for a fourth film, which had Riggs and Murtaugh dealing with neo-Nazi survivalists, who were launching a terrorist attack in Los Angeles. This script was written sometime in January of 1995, and according to Boam, it dealt with entire real-life neo-Nazi activity in the U.S., that was only superficially dealt with only one movie before, Dead Bang (1989). Despite the fact that everybody liked it, for some reason Boam's script was rejected, and Boam later said in interviews, how it was much better from the final movie, which suffered some problems with constant re-writes of the script that was chosen for the filming, and actually didn't have a completed script during filming.

The carpenter is named McGee. This is the actual surname of the actor portraying him, Jack McGee.

Shown unscheduled on Australian television, the night Nelson Mandela was elected President of South Africa, in May 1994.

Made over eighty-two million dollars more than the first movie domestically. Very unusual for a sequel, and also the most successful in the franchise, totaling 147.7 million dollars domestically.

Keith Haring's "Free South Africa" poster is seen in a few background shots, as it is in Scrooged (1988), also directed by Richard Donner.

When he was first hired to re-write Shane Black and Warren Murphy's original "Play Dirty" script for this movie, after it was rejected for being too dark and violent, Jeffrey Boam wrote two different drafts of his re-write; one which was a hard boiled action script, and one which had more comedy. He was told to mix both versions of his re-written script, and to make new draft from that. He still ended up having to constantly re-write the script before, and during filming, mostly because Richard Donner always wanted to improvise anything new while filming, or add something more, or different to the scene. Boam had to do the same with his script for Lethal Weapon 3 (1992) during filming of that movie. Another screenwriter, Robert Mark Kamen, mentioned in a 2012 interview for craveonline, how during the time when he was working as a screenwriter for Warner Brothers, and would often do lot of uncredited work on their films, he also worked on Lethal Weapon 2 and 3. He said how amongst a lot of the stuff he added in the Lethal Weapon 2 script during re-writes, were all the parts with the South African villains. Although he was uncredited for his work on this film, he did get a credit for his work on Lethal Weapon 3 (1992), because he did lot more work on that sequel.

The bottle of cologne that is shot during the destruction of Riggs' trailer is "Hero." The first time we see Riggs going into his trailer, there is an ad for that same cologne on television.

Joe Pantoliano was the first choice to play Leo, but he turned it down, due to a schedule conflict with The Last of the Finest (1990).

An alternate ending to the movie featured a Thanksgiving dinner at the Murtaugh house, which is attended by both Riggs and Rika Van Dan Haas. Richard Donner later decided that Rika should be killed, to further fuel Riggs' hatred of the South African diplomats. With Rika dead, this entire ending had to be scrapped. This ending was filmed prior to filming some of the other scenes from the film, including most of the second half, where Riggs and Murtaugh go into a final showdown with the South Africans. Another reason why this ending was not used, is because filmmakers weren't sure about whether Riggs should live or die at the end of the film.

George Harrison, Tom Petty, and Jeff Lynne (three-fifths of The Traveling Wilburys) composed "Cheer Down" for the soundtrack of this film.

Riggs is seen in his trailer watching The Three Stooges. Mel Gibson is a huge fan of The Three Stooges, because of their slapstick humor.

Danny DeVito was considered for the role of Leo Getz.

Rudd says that he lost over one million U.S. dollars in Krugerrand. The price of gold in 1989 was around four hundred dollars an ounce. It would take over 2,400 coins to equal that amount of money. One Krugerrand weighs 1.2 ounces (33.93 grams). The total weight of the coins would be just under one hundred eighty pounds.

While the Murtaugh family waits for the commercial, they watch Tales from the Crypt (1989), season one, episode two, Tales from the Crypt: And All Through the House (1989) (the psycho Santa episode), which aired on June 10, 1989, starring Mary Ellen Trainor, who plays police psychiatrist Dr. Stephanie Woods in the Lethal Weapon franchise. Some episodes in the series were produced by Richard Donner.

Gary Burghoff, of M*A*S*H (1972) fame, turned down the part of Leo Getz.

In the beginning chase scene, Riggs reads the license plate 24AdamHenry174, the "Adam Henry" part was an inside joke, being that it's a police movie. In police lingo, Adam Henry (AH) is an abbreviation for asshole.

The only Lethal Weapon movie which concludes straight after the final battle with the villains. The other three movies continue for a short time following the last battle.

Jenette Goldstein and Mark Rolston also appeared in Aliens (1986), as Vasquez and Drake, respectively.

In the opening scene, Riggs uses the Western Union phonetic alphabet ("Adam Henry") to report the license plate number, instead of the U.S. Military phonetic alphabet, which would be "Alpha Hotel".

During the toilet bomb scene, the police psychiatrist, Dr. Stephanie Woods (Mary Ellen Trainor), appears at the Murtaugh residence, however, Captain Murphy (Steve Kahan) does not. Of the 9 characters to appear in all 4 'Lethal Weapon' films (including Sam the Dog), Captain Murphy was the only one never to visit the Murtaugh residence at any point during any of the films.

The only film in the Lethal Weapon franchise in which Riggs drives a blue GMC Sierra. In the other films, Riggs drives a black GMC Sierra.

Principal photography took place in the spring of 1989.

Each Lethal Weapon film features a goon with glasses. Here, in the second one, it is the hitman, played by Paul Tuerpe, who appears in the scenes when Riggs shoots the fish tank, and when the hit squad attacks Riggs' trailer.

Mark Rolston (Hans) and Jenette Goldstein (Meagan Shapiro) also costarred as Colonial Marine privates Drake and Vasquez in Aliens (1986).

The only Lethal Weapon movie where Riggs doesn't hit with his left hand.

Throughout several points in the movie, Riggs willfully mispronounces Arjen Rudd's name as "Aryan", willfully calls Pieter Vorstedt "Adolf", and refers to Rudd, Vorstedt, and their associates as the "Master Race". These are all references to Adolf Hitler and the Nazis, before and during World War II. "Aryan Race" or "Master Race" was a Nazi ideological form, which became a concept for white supremacism. The South African practice of Apartheid at the time, was also another ideological form of white supremacy, which is likely why Riggs made these comparisons. Plus, the fact that Vorstedt looked like Adolf Hitler, helped make the nickname stick. In addition, when Rika (Patsy Kensit) hands the overnight faxes to her boss, Arjen Rudd (Joss Ackland), there is a stylized eagle on the wall behind him, reminiscent of the Reichsadler (the eagle clutching a swastika in its claws), a symbol of Nazi Germany, which was in turn based on the Aquila, the Roman eagle holding the SPQR symbol.

When the South African killer waiter gets out of the pool, Nakatomi Plaza from Die Hard can be seen in the background. Joel Silver produced both pictures.

The only Lethal Weapon sequel where the number in the title isn't in flames. The "2" appears bright red.

Even before suffering any collision damage, Murtagh's wife's station wagon has no rear view mirror. This is probably because many station waggons of that period had rear windows that could be wound down.

In June 1998, the pier set was still standing on the Warner Brothers backlot, as there was still concern that reshoots may have been required. The movie was released on July 10.

Leo is slang for Law Enforcement Officer. This may have been inspiration for the name Leo Getz.

Rika Van Den Haas (Patsy Kensit) was the only female worker at the South African Consulate.

Mel Gibson and Derrick O'Connor share the same birthday, January 3rd.

In the scene where Leo explains the money laundering scheme, Riggs wants Murtaugh to go find the house with him. He exclaims "You're black, I'm mad". As everyone knows, he plays Max "Mad Max" Rocketansky in the "Mad Max" movies.

The bulk cargo ship "Tequila Sunrise" stood in for Rudd's "Transvaal Lines" ship, "Alba Varden." The name can be seen on the bow as the camera pulls back. Mel Gibson starred in "Tequila Sunrise" with Kurt Russell.

The body count is thirty-three, the highest of the Lethal Weapon franchise.

Riggs intentionally dislocates his shoulder in this film, in order to get out of a straitjacket, then has to slam his shoulder back into place. This becomes a running gag throughout the franchise, where he slams his shoulder back into place after riding a motorcycle off a bridge in Lethal Weapon 3 (1992), and Ku (Jet Li's character) dislocates both of Riggs' shoulders in a fight scene in Lethal Weapon 4 (1998).

In the game Grand Theft Auto 5 (GTA 5), one the main protagonists finds out that his wife is cheating on him with a tennis coach. The house of the tennis coach is similar to the South African diplomat's house in the movie. In both the game and the movie, the protagonist brings down the house in a fit of rage by pulling one of the stilts on which the house is standing by using a pickup truck.

It is interesting to note that Riggs is cutting up fresh vegetables to put in the chili and yet the chili is from cans.

The only film as of 2019 in the series where Murtaugh kills the lead villain alone. It's Riggs and Murtaugh in the first film, and just Riggs in the third and fourth instalments.