A Pink's Eunji slapped Kim Jong Kook's forehead to complete a mission during this week's episode of 'Running Man'.

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During the show, the members of 'Running Man' were obligated to finish their own missions to win the whole game. 

For one of the missions, Kim Jong Kook had to get slapped by a female celebrity born in the 90s. To complete this, he met up with Eunji who was born in 1993. As soon as they met up, Kim Jong Kook proposed to play a game of rock, paper, scissors. He won 2 times in a row which made him flustered as he needed to lose in order to get slapped for the mission. On his last try, he finally lost and received a slap on the forehead he probably won't forget for a long time. 

Check out the funny clip above!