Robert Downey Jr and Writer/Director Shane Black, who both previously worked together on Kiss Kiss Bang Bang and Iron Man 3 were supposed to reunite for this however RDJ dropped out for unknown reasons and Mark Wahlberg replaced him.
The original draft for Lethal Weapon 2, written by Shane Black and Warren Murphy was titled "Play Dirty". Darker, grittier, and entirely different script compared to the finished film. Despite Fox studio's rejection of his original draft, Black considers his script for Lethal Weapon 2 to be his best work and most intense script he has ever written.