Ok Joo Hyun from the legendary girl group, Fin.K.L (Fine Killing Liberty), has made an appearance on Invincible Youth. Ok Joo Hyun was a surprise guest for the episode, and for this episode, she helped Kim Tae Woo made goo-chu-jang (red hot chili paste). Upon her arrival, the G7 members couldn't keep their poker faces on, as they were all delighted to meet their idol girl group senior. While the members were introducing themselves to Ok Joo Hyun, Yuri personally introduced Narsha by stating, "Adult idol Narsha." To add on, Kim Woo stated, "If you add up the Brown Eyed Girls' age, it exceeds 114 years." However, Ok Joo Hyun complimented on Narsha's feminine beauty by stating, "You can't get this kind of sexiness from a 20-year old." To this, Narsha responded, "I only look sloppy right now because I'm here, but when I'm on the stage, I'm alright." After her statement, she then went on to sing a verse from Fin.K.L's Forever Love, and concluded with an adult idol pose. [gallery]