Wonder World is the second studio album by South Korean pop girl group Wonder Girls. It was released on November 7, 2011. It was produced by Park Jin-Young. "Be My Baby" served as the lead single from album. Both album and single were commercial success. Album was promoted with a Wonder World Tour in 2012. Members were more involved in songwriting in production: Park Yeeun wrote and produced "G.N.O." and "Me, In", Kim Yubin wrote "Girls Girls", "Me, In" and "Sweet Dreams" while Woo Hyelim wrote and produced her solo song "Act Cool", featuring San E. Members also recorded duets: Min Sunye and Yeeun recorded "Long Long Time" while Yubin and Ahn Sohee recorded "SuperB".

On November 4, the album's name was revealed to be Wonder World, consisting of 11 new songs, one remixed song, and an English version of the lead single, "Be My Baby". Various members of the group contributed to composing material for the album. Park Yeeun was the composer and lyricist for the song "G.N.O." and performed the arrangement and composition for "Me, In". In an interview she commented about the strong American influence that she had received while working on new music in the album as she stated "When I went to a club, I heard songs from Rihanna and LMFAO. We thought it would be nice if we could make club music, done right, in Korean."Woo Hyelim collaborated with rapper San-E for her solo song "Act Cool" for which also helped her write the rap lyrics.Kim Yubin wrote the raps for the songs "Girls Girls" "Me, In" and "Sweet Dreams". Ahn Sohee and Yubin recorded a duet together called "SuperB", and Yeeun and Min Sunye also had a duet entitled "두고두고" (Long Long Time). Renowned choreographer Jonte' Moaning, who worked with American R&B artist Beyoncé on her song "Freakum Dress" and has served as a back-up dancer for "Single Ladies", helped choreograph the group's music video for "Be My Baby". Designer Johnny Wujek, who was also the fashion stylist for American pop artist Katy Perry's "I Kissed a Girl" and "California Gurls", also worked alongside the group.Wonder World placed at number 1 on the Gaon Weekly Album Chart and number 5 on Billboard's World Album Chart. "Be My Baby" went to number 1 on both the Gaon Weekly Digital Charts and the Billboard Korea K-Pop Hot 100. The song was also featured on the group's TV movie, "The Wonder Girls", which aired on TeenNick.

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