The most recent episode of SBS's "Strong Heart" guested a pair of celebrity siblings - Super Junior's Leeteuk and his sister, Park In Young. Leeteuk's sister became the talk of the town after she revealed her unexpected silly side. Park In Young was showing off her sexy appearance in her one-piece dress and leggings, when she suddenly broke out into a hilarious 'kkab' dance. Park then engaged in a dance off with the King of 'kkab' himself, 2AM's Jo Kwon! Leeteuk, who was embarrassed about having his older sister on air with him from the very beginning, couldn't take it anymore and shouted: "Nuna (older sister), don't do that!" - bringing much laughter. After the episode aired, viewers commented, "Her dance made even Jo Kwon's dance look colorless" and "Leeteuk's reaction was funnier." Source: Today Korea