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

And then the ultimate Cox-block.

J.D.

Dr. Cox: If you don't toss that shot back I'm gonna throw you on the counter and make you sing the theme song from 'Endless Love'.
J.D.: Yucky.
Dr. Cox: Yucky?
J.D.: Yucky.
Dr. Cox: Oh my God, I'm drinking with a Mousketeer

Scrubs Quotes

... Turk, Turk, Turk, Turk. I can't talk right now! I'm at your wedding.

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Doug: How long do I have to stay up here?
Janitor: Just until I finish pretending to read the newspaper. Hm! Apparently there was some sort of election held recently.