Wikipedia
D.O.C. (Lost)
"D.O.C." is the 18th episode of the 3rd season of Lost and the 67th episode overall. It was aired on April 25, 2007. The episode was written by Edward Kitsis and Adam Horowitz and directed by Fred Toye. The character of Sun-Hwa Kwon ( Yunjin Kim) is featured in the episode's flashbacks.
The title is a reference to the medical phrase of the same name which stands for 'Date of Conception', referring to the episode's plot of discovering Sun's D.O.C.
D.O.C. (Lost episode)