Who played J.D. in 'Scrubs'?

Who played Luke Danes in 'Gilmore Girls'? In which TV series is Luke Danes a main character? Who played Gil Grissom in 'CSI: Crime Scene Investigation'? In which TV series is Gil Grissom a main character? Who played Turk in 'Scrubs'? In which TV series is Turk a main character? Who played Dr. Perry Cox in 'Scrubs'? In which TV series is Dr. Perry Cox a main character?