Oh, hah! This is so funny. Well, I'll give you this lifeline: Ji Jin-hee is such a phenomenal actor, you can't even tell it's him in the part--he's the Korean Paul Muni, LOL.
Also, costuming for the historicals tends to obscure people, and you find yourself saying, "I know that guy..."
I thought Woojin was such a stinker when I first watched this (2003?), I didn't recognize him as Sir Min when I saw him there afterwards. Because I didn't like the character (Woojin), and what's not to like about Sir Min?
From Dae Jang-geum: Sun-dol: "Are you trying to dry me up and kill me? Why do you say the same things over and over every day? Rather, come and hit me once! Aigu!" But then: Dr. Lazarus: "By Grabthar's hammer, by the suns of Warvan... You shall be avenged."