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

Danni: You know what I was thinking?
J.D.: Nobody cares, Danni.

J.D.: Anyway, about this whole setting the date thing: I mean, I'm really psyched for you guys, it's just gonna be harder and harder for us to hang out, you know? I mean, you're gonna be married, man! You're gonna have, like, a house! You know? You're gonna be spending your weekends chasing around little Arturo and Rosaria!
Turk: You mean Tamika and Fuquan?
J.D.: You should... talk to Carla...

Scrubs Quotes

Turk: With Marbury, I really believe New York has a shot at the title, man.
J.D.: Yeah, me too.
Turk: Which sport are we talking about?
J.D.: I wanna say tennis...

J.D.: My man Turk, is getting it daily and nightly and ever so rightly! Ah! What up, dogg!
J.D.'s narration: Once every 4.2 seconds a man says something stupid that a woman hears and punishes him for... luckily, this wasn't one of those times.
Carla: What did you just say?
J.D.: "What up...dogg?"