Big cast changes on Criminal Minds caused fans to feel upset, like when JJ left season 6 due to financial reasons. JJ's return was supported by fan outcry and she became even more important in Season 7, bringing closure to her story. Despite struggles with pay disparities, A.J. Cook remained a leading character through the show's 15 seasons and future revival.

Criminal Minds was no stranger to cast turnover, losing key protagonists and going through a number of seasons in which team members seemed to arrive and leave within the same year. Many departures caused a stir among fans, and the reasons became well known, including the dismissal of Thomas Gibson after an alleged on-set altercation and the early loss of Mandy Patinkin as Jason Gideon over the show's content. One that was nearly as dramatic, however, was the departure and later return of A.J. Cook's Jennifer Jareau, better known as JJ.