Panabaker followed her initial appearances in commercials with roles in television, including a part in The Guardian (for which she won a Young Artist Award), as well as other television series including Malcolm in the Middle, Law & Order: Special Victims Unit, Medium, and Summerland, and the Disney Channel Original Movie Stuck in the Suburbs. She also appeared in the Lifetime Television productions Sex and the Single Mom and Mom at Sixteen, as well as the well-reviewed miniseries Empire Falls. She considers Empire Falls to be her big break, as it gave her the confidence to pursue her career. In addition, Panabaker appeared in stage productions with roles in musical theater, including West Side Story, Pippin, Once upon a Time, and Beauty Lou and the Country Beast. In 2004, she starred in the ABC film "Searching for David's Heart", alongside co-former Disney star Ricky Ullman. In 2005, Panabaker co-starred in two widely released theatrical films, Sky High and Yours, Mine and Ours. Her next role was in the film Home of the Giants (2008), opposite Ryan Merriman and Haley Joel Osment. She also had a supporting role in the film Mr. Brooks opposite Kevin Costner. In the Disney Channel original movie Read It and Weep, she plays Is, an alternate version of Jamie, who was played by her real-life sister Kay.