Doctor Jonathan Micheael "J.D." Dorian is the main character and narrator of Scrubs and is played by Zach Braff.  J.D. is best friends with Turk, who he's been friends with since they were roommates in college.  J.D. quickly meets Elliot, who he falls for hard and has an on and off again relationship with throughout the series. 

J.D.'s mentor is Dr. Cox who he is constantly trying to impress without making much headway.  He also has a bitter rival at Sacred Heart who torments him endlessly... The Janitor.  J.D. frequently daydreams where he tilts his head to the side and drifts away.

J.D. Quotes

Elliot: Now that you made out with my best friend, that makes us not even again. So go get me some cotton balls and a toe separator - mama needs a pedicure! Heh.
J.D.: Elliot, once you're even, you can't just go back to being not even. That ain't new, girl!
Elliot: Admit we're not even or I'll make you pay.
J.D.: Heh, yeah, now that we're friends and there's no chance of us ever having sex again, there's really not a whole lot I "need" from you, okay?

Dr. Kelso: Son, a hospital staff is like a melting pot! We all need to respect each other. Now, if you think that a specific ethnic group is loud or lazy or sneaky...
J.D.: Or ridiculously closed-minded and inappropriate...
Dr. Kelso: Exactly!... Just keep it to yourself, dammit!

Scrubs Quotes

Dr. Cox: Oh, you're gonna hang onto that?
Molly: Yeah, you know, I forgot my lunch money, and it's kielbasa day in the cafeteria. Kielbasa!

Dr. Kelso: Son, a hospital staff is like a melting pot! We all need to respect each other. Now, if you think that a specific ethnic group is loud or lazy or sneaky...
J.D.: Or ridiculously closed-minded and inappropriate...
Dr. Kelso: Exactly!... Just keep it to yourself, dammit!