Lee Seul Bi has a huge crush on her boss Lim Hyun Woo. One day, she drinks a cup of magical coffee that changes her appearance! Lee Seul Bi introduces herself as Oh Go Woon, a close friend of Lee Seul Bi and goes to work instead. Lim Hyun Woo knows that these two women look nothing alike, but he can't shake the feeling Oh Go Woon reminds him of Lee Seul Bi. Will Lee Seul Bi be able to keep her secret before her crush finds out the truth?
Producer duo Jeong Hyeong Don and Defconn unite four members from different K-pop groups, Jackson (GOT7), Sungjae (BtoB), N and Hyuk (Vixx) and create a new group, Big Byung, and produces a hit with them. (In the second season a new group is formed, but Big Byung makes a comeback with a second release in their appearance.)
Jung Hyung Don and Defconn recruited talents to form their own idol group. Their first idol unit group is made up of BtoB's Yook Sungjae, GOT7's Jackson and VIXX's N and Hyuk. In season 2 a new unit group is created with G.na, After School's Lizzy, 4minute's Kwon Sohyun and Kara's Heo Youngji.
"Monstar" depicts the lives of ordinary teens who are injured psychologically and heal themselves through the power of music. Yoon Sul-Chan is the vocalist for the group "Man in Black". He carries deep wounds within his mind, but doesn't express his feelings. Because of his hot temper, he causes trouble. His management company then orders him to carry himself as an ideal student. He joins a music band at school, while facing unexpected events.
Yong Jun-hyung (용준형), born Yong Jae-sun (용재순), is a South Korean singer active with the boyband, Beast. He has also worked under the stage names Joker and Poppin' Dragon.