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This cameo was even more special as Song Joong Ki was the one who personally asked the 'Giraffe' to make an appearance on the drama. The two actors are known to be best friends, so it came as no surprise when Lee Kwang Soo heartily agreed to Song Joong Ki's request. 

The crew commented on the the two's onscreen chemistry, stating, "Lee Kwang Soo immediately agreed on the cameo. The filming is already done, and even though [Lee Kwang Soo] only appeared for a brief time, he demonstrated a strong presence. Since they're so close, they flaunted a chemistry akin to that of rice cakes, which filled the set with lots of laughs." 

Just how good was the chemistry that the crew likened it to rice cakes? Better tune in to the drama to see the two in action when it airs later this year!