Murphy's breakthrough role was in her second feature film, the teen comedy "Clueless" (1995), directed by Amy Heckerling, which developed a cult following. She followed this with roles in "Freeway" (1996), with Reese Witherspoon and Kiefer Sutherland, and the independent comedy "Bongwater" (1998). In 1999, she had a supporting role in James Mangold's "Girl, Interrupted" as a troubled psychiatric patient alongside Winona Ryder and Angelina Jolie; and as an aspiring beauty queen in "Drop Dead Gorgeous". She also voiced the character Luanne Platter on Fox's animated sitcom "King of the Hill" for the entirety of the show's run from 1997 to 2009, and Joseph Gribble until the fifth season. She was nominated for an Annie Award for voice acting in the "King of the Hill" episode "Movin' On Up".