In 2011, she released her second single, "Going Crazy" featuring Bang Yong Guk which went to become her first number one single in the Gaon Charts as a solo artist.
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After Secret's great success with "Shy Boy", TS Entertainment announced that Jieun will make her solo comeback with the song "Going Crazy".
song | Eurovision Song Contest | Song Dynasty | My Way (song) | Eurovision Song Contest 2008 | Eurovision Song Contest 2013 | Academy Award for Best Original Song | Eurovision Song Contest 2009 | Eurovision Song Contest 2006 | Song | Eurovision Song Contest 2011 | A Nightingale Sang in Berkeley Square (song) | A Song of Ice and Fire | Viña del Mar International Song Festival | Eurovision Song Contest 2004 | The Song of Hiawatha | Song of the Year | Grammy Award for Song of the Year | Dream a Little Dream of Me (song) | Eurovision Song Contest 2007 | Song of the South | Cyprus in the Eurovision Song Contest | Song of Songs | Luxembourg in the Eurovision Song Contest | I've Got You Under My Skin (song) | Eurovision Song Contest 2010 | Creep (Radiohead song) | World Popular Song Festival | Space Oddity (song) | Song Sparrow |
On March 3, 2011 TS Entertainment revealed that Bang Yongguk will be the featured rapper in Song Jieun's "Going Crazy".
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In March 2011, he was featured in Song Jieun's Going Crazy and the single became a number one hit in South Korea.
Sunggyu made a cameo appearance in KBS's new sitcom A Bit of Love alongside four other idols, MBLAQ's G.O., KARA's Seungyeon, ZE:A's Siwan, and SECRET's Ji Eun.