Who played Dr. Perry Cox in 'Scrubs'?

In which TV series is Gil Grissom a main character? Who played J.D. in 'Scrubs'? Who played Turk in 'Scrubs'? In which TV series is Turk a main character? In which TV series is Dr. Perry Cox a main character? Who played Sydney Bristow in 'Alias'? In which TV series is Sydney Bristow a main character? Who played Clark Kent in 'Smallville'?