In July 2007, their third album, Insomniatic, was released, featuring the Billboard top 20 hit single, ' Potential Breakup Song'. In September 2006, they released a holiday album, Acoustic Hearts of Winter, featuring cover songs and two original songs. They released their first album, Into the Rush, on August 16, 2005.

Michalka and her sister AJ formed the musical duo Aly & AJ in 2004. On April 19, 2016, she was announced as a cast member for the comedy film The Lears, an adaptation based on the Shakespearean play King Lear. Michalka had a recurring role on the CW series iZombie for the first and second season, and became a regular cast member for season three. The movie was written and directed by her husband, Stephen Ringer, and premiered at the Los Angeles Film Festival on June 16, 2015. In July 2014, she and her sister filmed the independent drama Weepah Way for Now in Laurel Canyon, California Michalka also participated in the casting process and production for the film. In 2013, Michalka participated in a multi-episode role on the sitcom Two and a Half Men. In 2013, Michalka appeared in the independent drama film, Crazy Kind of Love, alongside Eva Longoria, Virginia Madsen and Amanda Crew. In 20 respectively, Michalka had major supporting roles in films Easy A and The Roommate. In 2011, Michalka made a guest appearance on CSI: NY. Despite a successful premiere, ratings dropped, and in May 2011, The CW announced the show was not renewed for a second season. In April 2010, The CW announced Michalka was cast in the main role of Marti Perkins on the cheerleading drama series Hellcats. In August 2009, she co-starred in the Walden Media film Bandslam. In 2007, they appeared in the MTV film Super Sweet 16: The Movie based on the MTV series My Super Sweet 16. Michalka and her sister starred in several projects produced by the Disney Channel and MTV. She has also starred in the Disney Channel original movie Now You See It., and appeared in the TV movie Cow Belles opposite her sister. In August 2006, Disney Channel ended the series after two seasons. In 2004, Michalka was cast in the role of Keely Teslow on the Disney Channel's Phil of the Future.

She started acting when she was five years old in church play productions. Michalka has played the piano since she was five and started playing the guitar at the age of 13. Her father, Mark, owns a contracting company, and her mother, Carrie, is a musician who performed with the Christian rock band 'JC Band'. She grew up in Seattle, Washington, and Southern California with her younger sister, Amanda Joy 'AJ', who is also an actress and musician. Michalka was born in Torrance, California.

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