Regarding his resemblance to child actor Kwak Dong-yeon

Regarding his resemblance to child actor Kwak Dong-yeon, Kim Hyun Joong said, 'A lot of people said my acting skills have improved after watching the child actor's performance (in the first 4 episodes). But I remained quiet about it. The reason for that is because we look alike. Even his mother couldn't differentiate us judging from our side face. Because he took on the role in the childhood episodes, viewers don't seem to realise the different after the transition to the adult episodes.'

Kim Hyun Joong, 'I always put in my best effort. Compared to previously, it seemed I have improved. I think it's better to have fun at the same time while filming. While having the conscious that I/we are actually acting, I think it's easier to grasp the character if we think ourselves as that person/character living in that era. I wanted to work hard on my acting skills and have fun filming too.'

Kim Sung-O, 'It's the first time I challenge such as action-studded drama so it's difficult to memorise the actions but Hyun Joong seemed to be able to memorise them easily. Memorising the movements is different from memorising the script lines. I find it difficult but Hyun Joong is good in it. It seemed like he is very clever. I envy him'
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Source: http://media.daum.net/entertain/drama/newsview?newsid=20140304140604353