Jeon So Min and Lee Kwang Soo get into it again on 'Running Man' this week

During one particular game on the October 29 show, the two actors got into it again. The point of the game was to maintain a smile after getting flicked on the forehead, a typical game in Korea. Lee Kwang Soo went first and hit Jeon So Min in the forehead but the actress wasn't able to keep her smile from the pain and failed.

Afterward, Lee Kwang Soo sat down and it now became Jeon So Min to flick his forehead. As a revenge, however, she decided to punch him after flicking him as she lacked power. Lee Kwang Soo immediately put on a straight face and was shocked at what she just did while the rest of the cast laughed at the funny situation. Lee Kwang Soo said, "With a fist like this...it's my first time ever being hit like this on the forehead...!"

Lee Kwang Soo and Jeon So Min truly seem like siblings!

SEE ALSO: Shindong shows off dramatic weight-loss results on JTBC’s ‘Knowing Bros’ “I’m finally in the double-digit range”