There are many ways to make a group of people diverse without giving them overly specialized roles within an ensemble. One way is through matching personality types according to a wacky ancient pseudoscience. The four temperaments (also called the “four humors”) was a theory that behavior was caused by concentrations of body fluids, the “humors” of classical medicine: blood, yellow bile, black bile, and phlegm. - TVTROPES 

Criminal Minds Characters + The Temperaments (Click on the gifs for some traits that the characters show that belong in that temperament) 

Criminal Minds characters based on zodiac signs

Aries: Derek Morgan

Taurus: Jason Gideon

Gemini: Elle Greenaway

Cancer: Jennifer Jareau

Leo: Dr Spencer Reid

Virgo: Aaron Hotchner

Libra: David Rossi

Scorpio: Alex Blake

Sagittarius: Kate Callahan

Aquarius: Emily Prentiss

Pisces: Penelope Garcia

Capricorn: Erin Strauss

Emily to Garcia: I know you don’t know Garcia, but I am alive. I stayed alive. And I will come home. One day I will come home. I promise, Penelope Garcia. And you, me and JJ will go out again and trick another “FBI” agent and spoil Henry rotten with coffee/shopping trips. Have faith and know that I won’t let you down.

Emily to Reid: Reid, you are like a brother to me, and I’m sorry I can’t tell you that I’m ok or good bye. But that’s just it, it isn’t good bye. Thank you for all that you have done for me. And for being you. There’s a lot to hate about you Dr. Reid, but even more importantly, there’s a lot to love.

Emily to Derek: Derek, where do I begin. Thank you for saving my life even after I told you not to profile me again. I’m sorry I lied, but I couldn’t tell you the truth. I just couldn’t bear the thought of more people getting hurt. Thank you for understanding.

Emily to JJ: JJ. You are so kind. Thank you for helping me, both in the saving of my life and the protection of Declan’s. I won’t let you down. PS How easy is it to un-die? Because when I come back, no more fake names. I want to be Emily Prentiss. 

Emily to Rossi: Rossi, you are like a wise, caring uncle, you always know when something’s up. I don’t know if you know, or suspect that I am alive. But either way, thanks for always listening and never judging.

Emily to Seaver: Ashley, you are going to be a great agent! I loved being able to share all that I have learned with this team with you. I’m sorry I can’t be at your graduation! Eat a cookie for me.

Emily to Hotch: Hotch, thanks for giving me a chance to be a part of this team 5 years ago. Now you know why I wanted it so much. We are similar in that, we profile because it’s who we are. Thank you for the opportunity to be a member of this family.