A bit of the cast were Korean pop stars. Such as Choi Minho from Shinee, and Kim Taehyung (V) from BTS
Park Seo Joon was the oldest, born in 1988, Kim Tae-Hyung/V was the youngest, born in 1995 Park Hyung-shik, Choi Minho, Do Ji-Han and Jo Yoon-woo were all born in 1991
Park Seo-Joon, Park Hyung-Sik and Kim Taehyung are part of the famous Wooga squad.
Three Hwarang actors are members of K-Pop groups.
Park Hyung-Sik (one of the main actors) is a member of ZE:A/ZE:A Five.
Choi Minho is a member of SHINee.
Kim Taehyung (aka V) is a member of Bangtan Sonyeondan, better known as BTS.
In one scene, the Hwarangs had to perform a sword dance. Choi Minho came up with the short choreography.