Main (Mad Dog) •
Yoo Ji-tae as Choi Kang-woo / Mad Dog :A former policeman and leader of the Mad Dog team. He has good eyes and sharp instincts, which help him achieve a 99% arrest rate. After meeting Kim Beom-joon's brother, he becomes suspicious of the reason for his wife and son's death, and so decides to re-investigate the case. •
Woo Do-hwan as Kim Min-joon / Jan Gebauer / Doctor Kim :A genius former swindler who was abandoned by his German foster parents. He has wits and good instincts, which allows him to transform into anybody. After 2 years, he returns to South Korea to prove his brother's innocence. •
Ryu Hwa-young as Jang Ha-ri / Player Jang :A former competing gymnast skilled at disguising herself in order to investigate insurance fraud schemes. •
Jo Jae-yoon as Park Soon-jung / Cheetah :An ex-thug with striking criminal records, who is now an insurance investigator that dreams of becoming a pediatric nurse for his love of children. •
Kim Hye-seong as On Nu-ri / Pentium :A computer genius who is allergic to the sun and hates going outside. •
Hong Soo-hyun as Cha Hong-joo :The only daughter of Cha Joon-kyu and Director of Taeyang Insurance. She has a crush on Kang-woo, but eventually decides to side with her father.
Supporting Taeyang Life Insurance •
Jeong Bo-seok as Cha Joon-kyu :Chairman of Taeyang Life Insurance. •
Jang Hyuk-jin as Park Moo-shin :Kang-woo's best friend who still works at Taeyang Insurance.
Juhan Airlines •
Choi Won-young as Joo Hyun-gi :Vice-president of JH Airlines. He is extremely cunning in planning strategies against his enemy.
Others •
Lee Jun-hyeok as Jo Han-woo :Kang-woo's fellow teammate back when he was a policeman. •
Park In-hwan as Byun Gook-jin •
Baek Ji-won as Oh Seo-ra •
Kim Young-hoon as Kim Bum-joon :Kim Min-joon's older brother. Co-pilot of the crashed JH 801, who was accused of crashing the plane on purpose to take his own life. •
Park Sung-hoon as Ko Jin Chul •
Park Min-jung as Lee Young-mi == Production ==