The opening credit Xmas tune is the exact same one as the original lethal weapon movie. Also the shirt Martin is wearing in the opening scene in the Xmas tree lot is also the same as the original movie
A car is driven forcefully right into Murtaugh's house causing substantial damage, much like at the end of the first LW film.
The music from the strip club is the same as the music from the stop club scene in Beverley Hills Cop. The Harrow club is also taken from the same movie, which was also a private up scale club
Murtaugh's famed "I'm too old for this...!" phrase from the films finally debuts, albeit without the expletive (this being a network TV show and all that).
At the strip club the song that is being played is the same song that is being played in the strip club in the movie Beverly Hills cop 2 (Nasty Girl)