When the MBC entertainment program 'Infinite Challenge' members asked Eun Ji Won what a pi (π) is, Eun Ji Won did not know what to say.

On the most recent episode of the popular MBC entertainment program 'Infinite Challenge,' which aired on October 2, 2015, Jung Joon Ha, Jung Hyung Don and Haha visited Eun Ji Won's house and tested his knowledge on mathematics, which turned out to be nonexistent. Jung Joon Ha, Jung Hyung Don and Haha asked Eun Ji Won some simple questions to test his candidacy for their "Idiot" mission. When it was turned out that he didn't know what pi was, Jung Joon Ha, Jung Hyung Don and Haha were happy that they have found the right candidate.

Prior to visiting Eun Ji Won's house, the six members teamed up in three pairs. Ha Ha and Kwanghee, Park Myung Soo and Jung Joon Ha, and Jung Hyung Don and Yoo Jae Suk became teams and brainstormed for ideas. The three pairs presented two to three ideas for the future MBC entertainment program 'Infinite Challenge' episodes. At the end of the presentation, Haha and Kwanghee's idea of "Idiot" competition won the first place, and the members split in threes and visited candidates. In related news, the MBC entertainment program 'Infinite Challenge' is one of the popular, long lasting entertainment programs in Korea. It features the Infinite Challenge members Ha Ha, Park Myung Soo, Yoo Jae Suk, Jung Joon Ha, and Jung Hyung Don.