The main cast of 'Running Man' have to complete as fast as possible all of the missions and quizzes (that's why they often have to run). Besides that, there might be a secret spy among Running Men;) and participants have to eliminate everyone to win the race (by tearing off a name tag of each person). Additionally, sometimes guests (such as actors, singers etc.) are invited to take part in the show, and they often get a secret mission;)
The program is really so funny^^ I recommend watching it: )
The main cast of 'Running Man':
1. Yoo Jae Seok [유재석], also known as Yooruce Willis, and Grasshopper. He is very very famous in Korea for being a great program's host (as in Infinite Challenge, Running Man), and also for being a great comedian.
3. Kim Jong Kook [김종국], known also as Commander or Sparta-Kook. Usually he is the most difficult to eliminate from the show. He is a singer.