Brittany Murphy was a voice artist.
Brittany Murphy-Monjack ( born Brittany Anne Bertolotti ; November 10 , 1977 -- December 20 , 2009 ) , known professionally as Brittany Murphy , was an American film and stage actress , singer , and voice artist . Murphy also voiced Luanne Platter on the animated television series King of the Hill ( 1997 -- 2009 ) .