The Wonder Girls debuted on February 10, 2007 on Show! Music Core, singing "Irony", the hip-hop single from their debut mini-album, The Wonder Begins. The mini-album
went on to become a minor hit, selling 11,454 copies in 2007. Throughout the rest of 2007, however, the Wonder Girls were beset by various injuries and health problems. On June 25, Sohee was sidelined for a month after tearing a knee ligament falling off a motorcycle during the filming of 뜨거운 것이 좋아 (I Like It Hot).The remaining four members continued performing until late July, when Hyuna was removed from the group due to their concern over her health—in particular, chronic gastroenteritis which had her hospitalized briefly in March and April.