In the pilot episode, in the beginning when we see Riggs' wife, Miranda, wave to the next door neighbor watering his lawn, the house behind him is the house the Murtaugh's lived in from the Lethal Weapon films.
In the pilot, Roger Murtaugh is said to have recently celebrated his 50th birthday. Damon Wayans turned 56 the month the pilot aired. Danny Glover was only 41 when the original movie premiered in 1987. Keesha Sharp, who plays Trish here is 13 years younger than Wayans, whereas Darlene Love, who played Trish in the movie was 8 years older than Glover. Mel Gibson was 31 in 1987, whereas Clayne Crawford was 38 as of the air date of the pilot.
Advertisements for this series credited Clayne Crawford as "Introducing Clayne Crawford" (a credit usually reserved for actors making a debut) even though Crawford had his first onscreen credit in 1997 (in an episode of "Buffy the Vampire Slayer") and has multiple credits per year, every year, since the early 2000s.
Damon Wayans, who plays Murtaugh, was the protagonist of The Last Boy Scout. Both The Last Boy Scout and the original Lethal Weapon film were written by Shane Black, meaning this is the second time Damon Wayans has played a Shane Black character.
In the third episode of season one, thieves rob an armored truck in almost the same method as the thieves from the film Heat (1995). Coincidentally, Ted Levine plays the armored truck driver in this episode, he also appeared as Bosko, one of the officers investigating the truck robbery thieves in Heat.
Prior to the series premiere, little known actor and producer Liam Fountain played Martin Rigg in a reenactment of a deleted scene from Lethal Weapon (1987). In 2011, Liam Fountain played Max Rockatansky in the short fan film Mad Max Renegade (2011). Martin Rigg and Max Rockatansky were played by Mel Gibson.
Jordana Brewster is famous for her role as Mia Toretto in the Fast and the Furious film franchise. In The Fast and the Furious (2001), Mia (Brewster) gets romantically involved with undercover police officer Brian O'Connor (Paul Walker).