 The 4th Season 1 episode "Dawg Days" was actually the third to be  filmed, and guest director Stephen Gyllenhaal had real trouble  establishing the proper look and characterization, only having the  pilot episode to go on as a reference point. Gyllenhaal and Michael  Chiklis in particular disagreed over how unsympathetically Vic  Mackie should be played, with Chiklis view winning out. The  decision was made after this that the writer of the episode would  always be on set to assist the director and actors.