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