On August 22 episode of SBS' television show 'My Little Old Boy', On Ju Wan made a guest appearance.

On Ju Wan responded, "Ah yes, I've actually known Ki-joon for a long time. But it was strange seeing him on set, because he wasn't like himself even when the cameras weren't rolling."
He continued, "He said hi to me like he was his character Joo Dan-tae. It was so weird. It seemed like he's basically been living like Joo Dan-tae for the last year and a half since the first season, even off camera."

The actor said, "There was this one scene where Kim So Yeon had to angrily give me something. While filming, she would be like, 'What did you just say?' and give me a death stare."
He resumed, "But as soon as the director says, 'Cut!' and I give the prop back to her for re-shooting, she turns into an angel. She's like, 'Oh, thank you. Thank you.' with such a kind smile."
He added, "I got so confused, because she would keep switching from evil Chun Seo-jin to angel Kim So Yeon within seconds. I just didn't know how to take that."

(Credit= SBS My Little Old Boy)
(SBS Star)