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

Lady: Love your Hairmet.
J.D.: Love yours!

J.D.: I was going to make you dinner and then go to karaoke but I don't know how to do both the same night...Unless of course...
Elliot: J.D., not floating head doctor.
J.D.: Too late, I'm already there.

Scrubs Quotes

Elliot: I'd like to remember all the carpal bones in the hand with a simple mnemonic device: Scaphoid, Lunate, Triquetral, Pisiform, Trapezium, Trapezoid, Capitate and Hamate. Some Lovers Try Positions That They Can't Handle.
Keith: Hey?!?!
Elliot: It was not directed at you, Doctor.

Dr. Kelso: Ahhh! Dr. Turkleton!
Turk: Actually, sir, it's Turk.
Dr. Kelso: That's your first name.
Turk: You think my name is Turk Turkleton?