Released on December 1, 2011, the album marks the first collaboration between the two away from their groups. The duo promoted the album extensively, including numerous performances. The song "Trouble Maker" was used to promote the EP. It was also performed at 2012 MAMA awards. The song won the Best Collaboration in the 14th Mnet Asian Music Awards.
The mini-album consists of 4 tracks; the title track "Trouble Maker", a ballad song called "The Words I Don't Want to Hear", a collaboration song from HyunA and Rado called "Time", and a solo song from Hyunseung called "Don't You Mind".
Trouble Maker won a MNet M! Countdown award for their song "Trouble Maker". The song also won the Mutizen Song on Inkigayo on January 8. As of December 31, 2012, the song has surpassed 4,408,787 paid downloads.
On November 24, Cube Entertainment announced that HyunA and Hyunseung would form a sub-unit. The agency also unveiled the unit's album jacket photo for their self-titled mini-album Trouble Maker. The photo features a private party concept which showcases Hyuna and Hyunseung dressed in black suits.
On November 26, 2011 Trouble Maker released the track listing for the then-upcoming debut album as well as an audio teaser. Hyuna and Hyunseung also performed at the 2011 Mnet Asian Music Awards to further promote the album, showcasing provocative dancing and what was believed to be an intimate kiss, forcing a Cube Entertainment official to make a statement that "[t]he kiss was not lip to lip, but actually lip to cheek."
On December 6, 2011 HyunA and Hyunseung performed as Trouble Maker at the United Cube concert in London as part of their promotional tour. They then moved onto Brazil a week later.
After promotions for Trouble Maker began, a large number of fans complained about HyunA and Hyunseung's racy choreography, and the duo were also forced to change their dance routine due to it being considered too sexy for national broadcast, with a new routine taking effect as of December 9's episode of KBS's Music Bank.
Since its release, it became an instant hit and its popularity soared. Numerous celebrities parodied "Trouble Maker", like in KBS's Dream High, where After School's Kahi and actor Kim Jung Tae replicated the "Trouble Maker" stage. From TV shows, concerts, award shows and more, it is common to see parodies of the duo showing how big an impression HyunA and Hyunseung made on the industry.
The first music video teaser was released on November 28, 2011, while the second one was released on November 29, 2011. The music video was released on December 1, 2011.
The "Trouble Maker" video plays on the cat-and-mouse theme. Set in a lavish hotel, the video is rife with gun play and sexual tension, with HyunA and Hyunseung "spying" on each other. At the end of the music video, HyunA sets the hotel room on fire, trapping Hyunseung. Hyunseung then shoots HyunA with a gun before she can leave. On October 27, 2013, the duo released the music video Now, which is a video showing HyunA and Hyunseung arguing and kissing in the scenes.