Brittany Murphy acted.
Brittany Murphy . Her later roles included Riding in Cars with Boys ( 2001 ) , Spun ( 2002 ) , Uptown Girls ( 2003 ) , Sin City ( 2005 ) , and Happy Feet ( 2006 ) . Murphy also voiced Luanne Platter on the animated television series King of the Hill ( 1997 -- 2009 ) .