 He later moved into dormitories with fellow trainees and was trained in areas of singing, acting, dancing as well as languages.He was featured in a music video of The Grace's Dana whilst he was being trained as a solo singer in 2003.A year after, Choi made a brief appearance in family drama, "Precious Family" and again in 2005 in the KBS romance comedy drama "Eighteen, Twenty-Nine" as young Kang Bong-man, while in 2006 he played the supporting role of Park Sang-woo in romance melodrama "Spring Waltz".