Every Major Cast Member of 'Criminal Minds' Throughout the Years

Joe plays David Rossi, a senior supervisory special agent for the BAU. He is considered one of the best profilers on the team and has authored several best-selling books on his work. In real life, Joe also has some impressive accolades, including a Tony Award and a star on the Hollywood Walk of Fame.

Paget made her debut as Emily Prentiss, a supervisory special agent and BAU Unit Chief, on season 2, but her role has been inconsistent since then. She left after season 7, was a guest on seasons 9 and 11, and returned as a main character during season 12. Paget has also appeared in a few episodes of Law & Order: Special Victims Unit.

Thomas was an original cast member, playing BAU unit chief and former senior supervisory special agent Aaron Hotchner on season 1. Thomas was "dismissed" from the series during filming for season 12 due to an altercation on set, according to The Hollywood Reporter. On the show, Aaron and his son were forced into the witness protection program, which is why he had to leave his job at the FBI.

Since the very beginning, Matthew has played Dr. Spencer Reid, a supervisory special agent who's a certified genius. Dr. Reid has several Ph.D.s, an extremely high IQ, and a photographic memory. Fun fact about Matthew: In real life, he's also an artist and sells his work on his website.

Kirsten started as the quirky and lovable Penelope Garcia, a technical analyst and communications liaison, on season 1. She is usually seen in her office, plugging away at her computer to support the rest of the team. Kirsten also plays Penelope on the spin-off, Criminal Minds: Suspect.

A.J. began as J.J., a supervisory special agent, way back on season 1. Although she briefly left during season 6, she returned as a regular on season 7. On the show, J.J. has two sons, who are actually played by A.J.'s real children!

Shemar debuted as supervisory special agent Derek Morgan in season 1, and left his role officially after season 11, though he appeared in a few episodes during seasons 12 and 13. His charismatic character is certainly missed, but Shemar is still active on the small screen, and currently plays Sergeant II Daniel "Hondo" Harrelson on S.W.A.T.

Aisha launched her role as forensic psychologist and supervisory special agent Dr. Tara Lewis on season 11. Although Aisha is relatively new to Criminal Minds, she has appeared in several notable shows, including Friends, The Talk, and CSI: Crime Scene Investigation.

Adam just joined the cast in season 12 as fugitive task force agent and supervisory special agent Luke Alvez, but it's certainly not his first well-known TV role. Many will remember him on CSI: Miami as Eric Delko.

Mandy played senior supervisory special agent and former BAU unit chief Jason Gideon on seasons 1 through 3, but Jason wasn't officially killed off the show until season 10. (Although it was off-screen.) Mandy now acts in Homeland as Saul Berenson.

Daniel began playing special operations agent Matthew Simmons on season 10 as a guest role, and officially joined the squad in season 13. He's also acted in Hawaii Five-0 and Criminal Minds: Beyond Borders.

Jennifer only appeared in season 10 of the procedural as undercover agent and supervisory special agent Kate Callahan. The actress originally went on maternity leave—which was also written into the show, so her character was pregnant—but decided not to return.