When a movie or television script calls for an actress to play a character who isn’t particularly attractive – the plain younger sister role, perhaps, or the overlooked personal assistant – the casting process is pretty simple: you give the part to a beautiful actress and you make her wear ugly glasses.
Then, at the appropriate moment in the story, she inadvertently removes her glasses and everyone sees just how stunning she really is, and the movie or television show moves quickly towards its happy and romantically satisfying conclusion...