Creator Backlash: Brian Garfield, the author of the original novel, sued the filmmakers for twisting the source material (ironically, the point of Garfield's novel was that vigilante tactics weren't the solution). You can probably guess from the four subsequent sequels that he lost.
The first movie has Jeff Goldblum in his screen debut playing one of the criminals who attack Kersey's wife and daughter. Denzel Washington and Sonia Manzano (Sesame Street's Maria) also have tiny bit parts; as a mugger and a grocery clerk respectively. Christopher Guest also appears as a patrolman.
Isaac Hayes was approached to do the music for the second film.
There were plans for a sixth film with the subtitle The New Vigilante.
As well as plans to bring back Kersey's girlfriend from the second film for a cameo in the third or fourth—to be killed off, of course.
One of the original drafted scripts for the fourth film was based around a plot involving Kersey playing two rival gangs against each other. Another one involved Kersey being secretly hired by the government to assassinate an international warlord.