Article: Criminal Minds
Section: Background

Question: Who plays FBI Agent Derek Morgan on the TV show "Criminal Minds"?

When the series premiered in 2005, it featured FBI Agents Jason Gideon (Mandy Patinkin), Aaron Hotchner (Thomas Gibson), Elle Greenaway (Lola Glaudini), Derek Morgan (Shemar Moore), Spencer Reid (Matthew Gray Gubler), Jennifer Jareau (A. J. Cook), and Penelope Garcia (Kirsten Vangsness).
During season one, Vangsness was not a part of the main cast, but instead appeared as a recurring star.
Since season two, she has been promoted to the main cast.
In season two (2006-07), Lola Glaudini announced her departure from the show, as she was unhappy living in Los Angeles and wished to return to Brooklyn.
She is replaced by Emily Prentiss (Paget Brewster), the daughter of an ambassador (Kate Jackson).
Although fans were initially wary of Lola Glaudini's departure, Paget Brewster's role in the show has received large praise from fans.
In season three, Patinkin announced his departure from the show, because he was deeply disturbed with the content depicted in the show.
He left apologetic letters for his fellow cast members explaining his reasons and wishing them luck.
He is replaced by David Rossi (Joe Mantegna), a former FBI agent and best-selling author.
Although fans were devastated with Mandy Patinkin's decision to leave, Joe Mantegna's role in the show has been well received, and fans eventually accepted him and his character.
In season four (2008-09), A. J. Cook became pregnant with her first child, fathered by her husband, Nathan Andersen.
Her pregnancy was written into the show, where Jennifer goes on maternity leave after giving birth to a son named Henry (played by A. J. Cook's real-life son, Mekhai Andersen).
Jordan Todd (Meta Golding), an FBI Agent from the Counterterrorism Unit, serves as Communications Liaison until Jennifer returns.
In season six, Jennifer is forced by Section Chief Erin Strauss (Jayne Atkinson) to accept a promotion at The Pentagon, causing her to leave the Behavioral Analysis Unit.
In episode ten, she is replaced by Ashley Seaver (Rachel Nichols), the daughter of a horrific serial killer known as "The Redmond Ripper".
Ashley transfers to the Domestic Trafficking Task Force after she graduates from the FBI academy.
Later in season six, Emily is seemingly killed off, although she actually survives, she does not appear at all for the rest of the season.
Also in season six, Jennifer returns twice as a special guest star.
In May 2011, CBS chose not to renew Rachel Nichols' contract for season seven (2011-12), due to her character's negative reception from fans.
The cause of A. J. Cook's and Paget Brewster's departure was CBS making a controversial decision to release them from their contracts, which caused numerous angry letters sent from the fans to the studio.
Because of this, A. J. Cook and Paget Brewster were re-hired by CBS, reprising as Jennifer Jareau and Emily Prentiss, respectively.
In February 2012, Paget Brewster announced her departure from the show after season seven and is replaced in season eight (2012-13) by Alex Blake (Jeanne Tripplehorn), a professor at Georgetown University.
Paget Brewster made a guest appearance in the show's 200th episode, reprising as Emily Prentiss.